The first thing it does is to set right the impression of the object, which is produced on the retina upside down. That original inversion is, as we know, brought about in the following manner. As each point of the visible objectsends forth its rays towards all sides in a rectilinear direction, the rays from its upper extremity cross those from its lower extremity in the narrow aperture of the pupil, by which the former impinge upon the bottom, the latter upon the top, those projected from the right side upon the left, andvice versa. The refracting apparatus of the eye, which consists of thehumor aqueus,lens,et corpus vitreum, only serves to concentrate the rays of light proceeding from the object, so as to find room for them on the small space of the retina. Now, if seeing consisted in mere sensation, we should perceive the impression of the object turned upside down, because we receive it thus; but in that case we should perceive it as something within our eye, for we should stop short at the sensation. In reality, however, the Understanding steps in at once with its causal law, and as it has received from sensation the datum of the direction in which the ray impinged upon the retina, it pursues that direction retrogressively up to the cause on both lines; so that this time the crossing takes place in the opposite direction, and the cause presents itself upright as an external object in Space,i.e.in the position in which it originally sent forth its rays, not that in which they reached the retina (see fig. 1).—The purely intellectual nature of this process, to the exclusion of all other, more especially of physiological, explanations, may also be confirmed by thefact, that if we put our heads between our legs, or lie down on a hill head downwards, we nevertheless see objects in their right position, and not upside down; although the portion of the retina, which is usually met by the lower part of the object is then met by the upper: in fact, everything is topsy turvy excepting the Understanding.rays entering the retina of the eyeFig. 1.Thesecondthing which the Understanding does in converting sensation into perception, is to make a single perception out of a double sensation; for each eye in fact receives its own separate impression from the object we are looking at; each even in a slightly different direction: nevertheless that object presents itself as a single one. This can only take place in the Understanding, and the process by which it is brought about is the following: Our eyes are never quite parallel, excepting when we look at a distant object,i.e.one which is more than 200 feet from us. At other times they are both directed towards the object we are viewing, whereby they converge, so as to make the lines proceeding from each eye to the exact point of the object on which it is fixed, form anangle, called theoptic angle; the lines themselves are calledoptic axes. Now, when the object lies straight before us, these lines exactly impinge upon the centre of each retina, therefore in two points which correspond exactly to each other in each eye. The Understanding, whose only business it is to look for thecauseof all things, at once recognises the impression as coming from asingleoutside point, although here the sensation is double, and attributes it toonecause, which therefore presents itself as a single object. For all that is perceived by us, is perceived as acause—that is to say, as the cause of an effect we have experienced, consequentlyin the Understanding. As, nevertheless, we take in not only a single point, but a considerable surface of the object with both eyes, and yet perceive it as a single object, it will be necessary to pursue thisexplanation still further. All those parts of the object which lie to one side of the vertex of the optic angle no longer send their rays straight into the centre, but to the side, of the retina in each eye; in both sides, however, to the same, let us say the left, side. The points therefore upon which these rays impinge,correspond symmetrically to each other, as well as the centres—in other words, they arehomonymous points. The Understanding soon learns to know them, and accordingly extends the above-mentioned rule of its causal perception to them also; consequently it not only refers those rays which impinge upon the centre of each retina, but those also which impinge upon all the other symmetrically corresponding places in both retinas, to a single radiant point in the object viewed: that is, it sees all these points likewise as single, and the entireobject also. Now, it should be well observed, that in this process it is not the outer side of one retina which corresponds to the outer side of the other, and the inner to the inner of each, but the right side of one retina which corresponds to the right side of the other, and so forth; so that this symmetrical correspondence must not be taken in a physiological, but in a geometrical sense. Numerous and very clear illustrations of this process, and of all the phenomena which are connected with it, are to be found in Robert Smith's "Optics," and partly also in Kästner's German translation (1755). I only giveone(fig. 2), which, properly speaking, represents a special case, mentioned further on, but which may also serve to illustrate the whole, if we leave the point R out of question. According to this illustration, we invariably direct both eyes equally towards the object, in order that the symmetrically corresponding places on both retinas may catch the rays projected from the same points. Now, when we move our eyes upwards and downwards, to the sides, and in all directions, the point in the object which first impinged upon the central point of each retina, strikes a different place every time, but in all cases one which, in each eye, corresponds to the place bearing the same name in the other eye. In examining (perlustrare) an object, we let our eyes glide backwards and forwards over it, in order to bring each point of it successively into contact with the centre of the retina, which sees most distinctly: we feel it all over with our eyes. It is therefore obvious that seeing singly with two eyes is in fact the same process as feeling a body with ten fingers, each of which receives a different impression, each moreover in a different direction: the totality of these impressions being nevertheless recognised by the Understanding as proceeding fromoneobject, whose shape and size it accordingly apprehends and constructs in Space. This is why it is possible for a blind man to becomea sculptor, as was the case, for instance, with the famous Joseph Kleinhaus, who died in Tyrol, 1853, having been a sculptor from his fifth year.[80]For, no matter from what cause it may have derived its data, perception is invariably an operation of the Understanding.the symmetry of the raysFig. 2.But just as a single ball seems to me double, if I touch it with my fingers crossed—since my Understanding, at once reverting to the cause and constructing it according to the laws of Space, takes for granted that the fingers are in their normal position and of course cannot do otherwise than attribute two spherical surfaces, which come in contact with the outer sides of the first and middle fingers, to two different balls—just so also does an object seem double, if my eyes, instead of converging symmetrically and enclosing the optic angle at a single point of the object, each view it at a different inclination—in other words, if I squint. For the rays, which in this case emanate from one point of the object, no longer impinge upon those symmetrically corresponding points in both retinas with which my mind has grown familiar by long experience, but upon other, quite different ones which, in a symmetrical position of the eyes, could only be affected in this way by differentbodies; I therefore now seetwoobjects, precisely because perception takes place by means of, and within, the Understanding.—The same thing happens without squinting when, for instance, I look fixedly at the furthest of two objects placed at unequal distances before me, and complete the optic angle at it; for then the rays emanating from the nearer object do not impinge upon symmetrically corresponding places in both retinas, wherefore my Understanding attributes them to two objects,i.e.I see the nearer object double (see fig. 2, page 70). If, on the contrary, I complete the optic angle at the nearer object, by looking steadily at it, the further object appears double. It is easy to test this by holding a pencil two feet from the eyes, and looking alternately at it and at some other more distant object behind it.But the finest thing of all is, that this experiment may quite well be reversed: so that, with two real objects straight before and close to us, and with our eyes wide open, we nevertheless see butone. This is the most striking proof that perception is a work of the Understanding and by no means contained in sensation. Let two cardboard tubes, about 8 inches long and 1-1/2 inches in diameter, be fastened parallel to one another, like those of a binocular telescope, and fix a shilling at the end of each tube. On applying our eyes to the opposite extremity and looking through the tubes, we shall see onlyoneshilling surrounded byonetube. For in this case the eyes being forced into a completely parallel position, the rays emanating from the coins impinge exactly upon the centres of the two retinas and those points which immediately surround them, therefore upon places which correspond symmetrically to each other; consequently the Understanding, taking for granted the usual convergent position of the optic axes when objects are near, admits but one object as the cause of the reflected rays. In other words, we see butone object; so direct is the act of causal apprehension in the Understanding.We have not space enough here to refute one by one the physiological explanations of single vision which have been attempted; but their fallacy is shown by the following considerations:—1o. If seeing single were dependent upon an organic connection, the corresponding points in both retinas, on which this phenomenon is shown to depend, would correspondorganically, whereas they do so in a merelygeometricalsense, as has already been said. For, organically speaking, the two inner and two outer corners of the eyes are those which correspond, and so it is with the other parts also; whereas for the purpose of single vision, it is the right side of the right retina which corresponds to the right side of the left retina, and so on, as the phenomena just described irrefutably show. It is also precisely on account of the intellectual character of the process, that only the most intelligent animals, such as the higher mammalia and birds of prey—more especially owls—have their eyes placed so as to enable them to direct both optic axes to the same point.2o. The hypothesis of a confluence or partial intersection of the optic nerves before entering the brain, originated by Newton,[81]is false, simply because it would then be impossible to see double by squinting. Vesalius and Cæsalpinus besides have already brought forward anatomical instances in which subjects saw single, although neither fusion nor even contact of the optic nerves had taken place. A final argument against the hypothesis of a mixed impression is supplied by the fact, that on closing our right eye firmly and looking at the sun with our left, the bright image which persists for a time is always in the left, never in the right, eye: andvice versa.Thethirdprocess by which the Understanding converts sensation into perception, consists in constructing bodies out of the simple surfaces hitherto obtained—that is, in adding the third dimension. This it does by estimating the expansion of bodies in this third dimension in Space—which is known to the Understandingà priori—through Causality, according to the degree in which the eye is affected by the objects, and to the gradations of light and shade. In fact, although objects fill Space in all three dimensions, they can only produce an impression upon the eye with two; for the nature of that organ is such, that our sensation, in seeing, is merely planimetrical, not stereometrical. All that is stereometrical in our perception is added by the Understanding, which has for its sole data the direction whence the eye receives its impression, the limits of that impression, and the various gradations of light and dark: these data directly indicate their causes, and enable us to distinguish whether what we have before us is a disk or a ball. This mental process, like the preceding ones, takes place so immediately and with such rapidity, that we are conscious of nothing but the result. It is this which makes perspective drawing so difficult a problem, that it can only be solved by mathematics and has to be learnt; although all it has to do, is to represent the sensation of seeing as it presents itself to our Understanding as a datum for the third process: that is, visual sensation in its merely planimetrical extension, to thetwodimensions of which extension, together with the said data in them, the Understanding forthwith adds thethird, in contemplating a drawing as well as in contemplating reality. Perspective drawing is, in fact, a sort of writing which can be read as easily as printed type, but which few are able to write; precisely because our intellect, in perceiving, only apprehends effects with a view to constructing their causes, immediately losing sight of the former as soon as it hasdiscovered the latter. For instance, we instantly recognise a chair, whatever position it may be in; while drawing a chair in any position belongs to the art which abstracts from this third process of the Understanding, in order to present the data alone for the spectator himself to complete. In its narrowest acceptation, as we have already seen, this is the art of drawing in perspective; in a more comprehensive sense, it is the whole art of painting. A painting presents us with outlines drawn according to the rules of perspective; lighter and darker places proportioned to the effect of light and shade; finally patches of colouring, which are determined as to quality and intensity by the teaching of experience. This the spectator reads and interprets by referring similar effects to their accustomed causes. The painter's art consists in consciously retaining the data of visual sensation in the artist's memory, as they arebeforethis third intellectual process; while we, who are not artists, cast them aside without retaining them in our memory, as soon as we have made use of them for the purpose described above. We shall become still better acquainted with this third intellectual process by now passing on to a fourth, which, from its intimate connection with the third, serves to elucidate it.Thisfourthoperation of the Understanding consists in acquiring knowledge of the distance of objects from us: it is this precisely which constitutes that third dimension of which we have been speaking. Visual sensation, as we have said, gives us thedirectionin which objects lie, but not theirdistancefrom us: that is, not theirposition. It is for theUnderstandingtherefore to find out this distance; or, in other words, the distance must be inferred from purelycausaldeterminations. Now the most important of these is thevisual angle, which objects subtend; yet even this is quite ambiguous and unable to decide anything by itself. It is like a word of double meaning:the sense, in which it is to be understood, can only be gathered from its connection with the rest. An object subtending the same visual angle may in fact be small and near, or large and far off; and it is only when we have previously ascertained its size, that the visual angle enables us to recognise its distance: and conversely, its size, when its distance is known to us. Linear perspective is based upon the fact that the visual angle diminishes as the distance increases, and its principles may here be easily deduced. As our sight ranges equally in all directions, we see everything in reality as from the interior of a hollow sphere, of which our eye occupies the centre. Now in the first place, an infinite number of intersecting circles pass through the centre of this sphere in all directions, and the angles measured by the divisions of these circles are the possible angles of vision. In the second place, the sphere itself modifies its size according to the length of radius we give to it; therefore we may also imagine it as consisting of an infinity of concentric, transparent spheres. As all radii diverge, these concentric spheres augment in size in proportion to their distance from us, and the degrees of their sectional circles increase correspondingly: therefore the true size of the objects which occupy them likewise increases. Thus objects are larger or smaller according to the size of the spheres of which they occupy similar portions—say 10°—while their visual angle remains unchanged in both cases, leaving it therefore undecided, whether the 10° occupied by a given object belong to a sphere of 2 miles, or of 10 feet diameter. Conversely, if the size of the object has been ascertained, the number of degrees occupied by it will diminish in proportion to the distance and the size of the sphere to which we refer it, and all its outlines will contract in similar proportion. From this ensues the fundamental law of all perspective; for, as objects and the intervals between them must necessarilydiminish in constant proportion to their distance from us, all their outlines thereby contracting, the result will be, that with increasing distance, what is above us will descend, what is below us will ascend, and all that lies at our sides will come nearer together. This progressive convergence, this linear perspective, no doubt enables us to estimate distances, so far as we have before us an uninterrupted succession of visibly connected objects; but we are not able to do this by means of the visual angle alone, for here the help of another datum is required by the Understanding, to act, in a sense, as commentary to the visual angle, by indicating more precisely the share we are to attribute to distance in that angle. Now there are four principal data of this kind, which I am about to specify. Thanks to these data, even where there is no linear perspective to guide us, if a man standing at a distance of 200 feet appears to me subtending a visual angle twenty-four times smaller than if he were only 2 feet off, I can nevertheless in most cases estimate his size correctly. All this proves once more that perception is not only a thing of the senses, but of the intellect also.—I will here add the following special and interesting fact in corroboration of what I have said about the basis of linear perspective as well as about the intellectual nature of all perception. When I have looked steadily at a coloured object with sharply defined outlines—say a red cross—long enough for the physiological image to form in my eye as a green cross, the further the surface on to which I project it, the larger it will appear to me: andvice versa. For the image itself occupies an unvarying portion of my retina,i.e.the portion originally affected by the red cross; therefore when referred outwards, or, in other words, recognised as the effect of an external object, it forms an unchanging visual angle, say of 2°. Now if, in this case, where all commentary to the visual angle is wanting, I remove it toa distant surface, with which I necessarily identify it as belonging to its effect, the cross will occupy 2° of a distant and therefore larger sphere, and is consequently large. If, on the other hand, I project the image on to a nearer object, it will occupy 2° of a smaller sphere, and is therefore small. The resulting perception is in both cases completely objective, quite like that of an external object; and as it proceeds from an entirely subjective reason (from the image having been excited in quite a different way), it thus confirms the intellectual character of all objective perception.—This phenomenon (which I distinctly remember to have been the first to notice, in 1815) forms the theme of an essay by Séguin, published in the "Comptes rendus" of the 2nd August, 1858, where it is served up as a new discovery, all sorts of absurd and distorted explanations of it being given.Messieurs les illustres confrèreslet pass no opportunity for heaping experiment upon experiment, the more complicated the better.Expérience!is their watchword; yet how rarely do we meet with any sound, genuine reflection upon the phenomena observed!Expérience! expérience!followed by twaddle.To return to the subsidiary data which act as commentaries to a given visual angle, we find foremost among them themutationes oculi internæ, by means of which the eye adapts its refractory apparatus to various distances by increasing and diminishing the refraction. In what these modifications consist, has not yet been clearly ascertained. They have been sought in the increased convexity, now of thecornea, now of the crystallinelens; but the latest theory seems to me the most probable one, according to which the lens is moved backwards for distant vision and forwards for near vision, lateral pressure, in the latter case, giving it increased protuberance; so that the process would exactly resemble the mechanism of an opera-glass.Kepler, however, had, in the main, already expressed this theory, which may be found explained in A. Hueck's pamphlet, "Die Bewegung der Krystallinse," 1841. If we are not clearly conscious of these inner modifications of the eye, we have at any rate a certain feeling of them, and of this we immediately avail ourselves to estimate distances. As however these modifications are not available for the purposes of clear sight beyond the range of from about 7 inches to 16 feet, the Understanding is only able to apply this datum within those limits.Beyond them, however, the second datum becomes available: that is to say, theoptic angle, formed by the two optic axes, which we had occasion to explain when speaking of single vision. It is obvious that this optic angle becomes smaller, the further the object is removed: andvice versa. This different direction of the eyes, with respect to each other, does not take place without producing a slight sensation, of which we are nevertheless only in so far conscious as the Understanding makes use of it, as a datum, in estimating distances intuitively. By this datum we are not only enabled to cognize the distance, but the precise position of the object viewed, by means of the parallax of the eyes, which consists in each eye seeing the object in a slightly different direction; so that if we close one eye, the object seems to move. Thus it is not easy to snuff a candle with one eye shut, because this datum is then wanting. But as the direction of the eyes becomes parallel as soon as the distance of the object reaches or exceeds 200 feet, and as the optic angle consequently then ceases to exist, this datum only holds good within the said distance.Beyond it, the Understanding has recourse toatmospheric perspective, which indicates a greater distance by means of the increasing dimness of all colours, of the appearance of physical blue in front of all dark objects(according to Göthe's perfectly correct and true theory of colours), and also of the growing indistinctness of all outlines. In Italy, where the atmosphere is very transparent, this datum loses its power and is apt to mislead: Tivoli, for instance, seems to be very near when seen from Frascati. On the other hand, all objects appear larger in a mist, which is an abnormal exaggeration of the datum; because our Understanding assumes them to be further from us.Finally, there remains the estimation of distance by means of the size (known to us intuitively) of intervening objects, such as fields, woods, rivers, &c. &c. This mode of estimation is only applicable where there is uninterrupted succession: in other words, it can only be applied to terrestrial, not to celestial objects. Moreover, we have in general more practice in using it horizontally than vertically: a ball on the top of a tower 200 feet high appears much smaller to us than when lying on the ground 200 feet from us; because, in the latter case, we estimate the distance more accurately. When we see human beings in such a way, that what lies between them and ourselves is in a great measure hidden from our sight, they always appear strikingly small.The fact that our Understanding assumes everything it perceives in a horizontal direction to be farther off, therefore larger, than what is seen in a vertical direction, must partly be attributed to this last mode of estimating distances, inasmuch as it only holds good when applied horizontally and to terrestrial objects; but partly also to our estimation of distances by atmospheric perspective, which is subject to similar conditions. This is why the moon seems so much larger on the horizon than at its zenith, although its visual angle accurately measured—that is, the image projected by it on to the eye—is not at all larger in one case than in the other; and this also accounts for the flattened appearance ofthe vault of the sky: that is to say, for its appearing to have greater horizontal than vertical extension. Both phenomena therefore are purely intellectual or cerebral, not optical. If it be objected, that even when at its zenith, the moon occasionally has a hazy appearance without seeming to be larger, we answer, that neither does it in that case appear red; for its haziness proceeds from a greater density of vapours, and is therefore of a different kind from that which proceeds from atmospheric perspective. To this may be added what I have already said: that we only apply this mode of estimating distances in a horizontal, not in a perpendicular, direction; besides, in this case, other correctives come into play. It is related of Saussure that, when on the Mont Blanc, he saw so enormous a moon rise, that, not recognising what it was, he fainted with terror.The properties of the telescope and magnifying glass, on the other hand, depend upon a separate estimate according to the visual angle alone:i.e., that of size by distance, and of distance by size; because here the four other supplementary means of estimating distances are excluded. The telescope in reality magnifies objects, while it only seems to bring them nearer; because their size being known to us empirically, we here account for its apparent increase by a diminution of their distance from us. A house seen through a telescope, for instance, seems to be ten times nearer, not ten times larger, than seen with the naked eye. The magnifying glass, on the contrary, does not really magnify, but merely enables us to bring the object nearer to our eyes than would otherwise be possible; so that it only appears as large as it would at that distance even without the magnifying glass. In fact, we are prevented from seeing objects distinctly at less than from eight to ten inches' distance from our eyes, by the insufficient convexity of the ocularlens and cornea; but if we increase the refraction by substituting the convexity of the magnifying glass for that of the lens and cornea, we then obtain a clear image of objects even when they are as near as half an inch from our eyes. Objects thus seen in close proximity to us and in the size corresponding to that proximity, are transferred by our Understanding to the distance at which we naturally see distinctly,i.e.to about eight or ten inches from our eyes, and we then estimate their magnitude according to this distance and to the given visual angle.I have entered thus fully into detail concerning all the different processes by which seeing is accomplished, in order to show clearly and irrefragably that the predominant factor in them isthe Understanding, which, by conceiving each change as aneffectand referring that effect to itscause, produces the cerebral phenomenon of the objective world on the basis of theà priorifundamental intuitions of Space and Time, for which it receives merely a few data from the senses. And moreover the Understanding effects this exclusively by means of its own peculiar form, the law of Causality; therefore quite directly and intuitively, without any assistance whatever from reflection—that is, from abstract knowledge by means of conceptions and of language, which are the materials ofsecondaryknowledge,i.e.ofthought, therefore ofReason.That this knowledge through the Understanding is independent of Reason's assistance, is shown even by the fact, that when, at any time, the Understanding attributes a given effect to a wrong cause, actually perceiving that cause, wherebyillusionarises, our Reason, however clearly it may recognisein abstractothe true state of the matter, is nevertheless unable to assist the Understanding, and the illusion persists undisturbed in spite of that better knowledge. The above-mentioned phenomena of seeing and feeling double, which result from an abnormal positionof the organs of touch and sight, are instances of such illusions; likewise the apparently increased size of the rising moon; the image which forms in the focus of a concave mirror and exactly resembles a solid body floating in space; the painted relievo which we take for real; the apparent motion of a shore or bridge on which we are standing, if a ship happens to pass along or beneath it; the seeming proximity of very lofty mountains, owing to the absence of atmospheric perspective, which is the result of the purity of the air round their summits. In these and in a multitude of similar cases, our Understanding takes for granted the existence of the usual cause with which it is conversant and forthwith perceives it, though our Reason has arrived at the truth by a different road; for, the knowledge of the Understanding being anterior to that of the Reason, the intellect remains inaccessible to the teaching of the Reason, and thus theillusion—that is, the deception of the Understanding—remains immovable; albeiterror—that is, the deception of the Reason—is obviated.—That which is correctly known by the Understanding isreality: that which is correctly known by the Reason istruth, or in other terms, a judgment having a sufficient reason;illusion(that which is wrongly perceived) we oppose toreality:error(that which is wrongly thought) totruth.The purely formal part of empirical perception—that is, Space, Time, and the law of Causality—is containedà prioriin the intellect; but this is not the case with the application of this formal part to empirical data, which has to be acquired by the Understanding through practice and experience. Therefore new-born infants, though they no doubt receive impressions of light and of colour, still do not apprehend or indeed, strictly speaking, see objects. The first weeks of their existence are rather passed in a kind of stupor, from which they awaken by degrees when their Understanding begins to apply its function to thedata supplied by the senses, especially those of touch and of sight, whereby they gradually gain consciousness of the objective world. This newly-arising consciousness may be clearly recognised by the look of growing intelligence in their eyes and a degree of intention in their movements, especially in the smile with which they show for the first time recognition of those who take care of them. They may even be observed to make experiments for a time with their sight and touch, in order to complete their apprehension of objects by different lights, in different directions and at different distances: thus pursuing a silent, but serious course of study, till they have succeeded in mastering all the intellectual operations in seeing which have been described. The fact of this schooling can be ascertained still more clearly through those who, being born blind, have been operated upon late in life, since they are able to give an account of their impressions. Cheselden's blind man[82]was not an isolated instance, and we find in all similar cases the fact corroborated, that those who obtain their sight late in life, no doubt, see light, outlines, and colours, as soon as the operation is over, but that they have no objective perception of objects until their Understanding has learnt to apply its causal law to data and to changes which are new to it. On first beholding his room and the various objects in it, Cheselden's blind man did not distinguish one thing from another; he simply received the general impression of a totality all in one piece, which he took for a smooth, variegated surface. It never occurred to him to recognise a number of detached objects, lying one behind the other at different distances. With blind people of this sort, it is by the sense of touch, to which objects are already known, that they have to be introduced to the sense ofsight. In the beginning, the patient has no appreciation whatever of distances and tries to lay hold of everything. One, when he first saw his own house from outside, could not conceive how so small a thing could contain so many rooms. Another was highly delighted to find, some weeks after the operation, that the engravings hanging on the walls of his room represented a variety of objects. The "Morgenblatt" of October 23rd, 1817, contains an account of a youth who was born blind, and obtained his sight at the age of seventeen. He had to learn intelligent perception, for at first sight he did not even recognise objects previously known to him through the sense of touch. Every object had to be introduced to the sense of sight by means of the sense of touch. As for the distances of the objects he saw, he had no appreciation whatever of them, and tried to lay hold indiscriminately of everything, far or near.—Franz expresses himself as follows:[83]—"A definite idea of distance, as well as of form and size, is only obtained by sight and touch, and by reflecting on the impressions made on both senses; but for this purpose we must take into account the muscular motion and voluntary locomotion of the individual.—Caspar Hauser, in a detailed account of his own experience in this respect, states, that upon his first liberation from confinement, whenever he looked through the window upon external objects, such as the street, garden, &c., it appeared to him as if there were a shutter quite close to his eye, and covered with confused colours of all kinds, in which he could recognise or distinguish nothing singly. He says farther, that he did not convince himself till after some time during his walks out of doors, that what had at first appeared to him as a shutter of various colours, as well as many other objects, were in reality very different things; and that at length the shutter disappeared, and he saw and recognised all things in their just proportions. Persons born blind who obtain their sight by an operation in later years only, sometimes imagine that all objects touch their eyes, and lie so near to them that they are afraid of stumbling against them; sometimes they leap towards the moon, supposing that they canlay hold of it; at other times they run after the clouds moving along the sky, in order to catch them, or commit other such extravagancies. Since ideas are gained by reflection upon sensation, it is further necessary in all cases, in order that an accurate idea of objects may be formed from the sense of sight, that the powers of the mind should be unimpaired, and undisturbed in their exercise. A proof of this is afforded in the instance related by Haslam,[84]of a boy who had no defect of sight, but was weak in understanding, and who in his seventh year was unable to estimate the distances of objects, especially as to height; he would extend his hand frequently towards a nail on the ceiling, or towards the moon, to catch it. It is therefore the judgment which corrects and makes clear this idea, or perception of visible objects."The intellectual nature of perception as I have shown it, is corroborated physiologically by Flourens[85]as follows:"Il faut faire une grand distinction entre les sens et l'intelligence. L'ablation d'un tubercule détermine la perte de lasensation, dusensde la vue; la rétine devient insensible, l'iris devient immobile. L'ablation d'un lobe cérébral laisse lasensation, lesens, lasensibilitéde la rétine, lamobilitéde l'iris; elle ne détruit que laperceptionseule. Dans un cas, c'est un faitsensorial; et, dans l'autre, un faitcérébral; dans un cas, c'est la perte dusens; dans l'autre, c'est la perte de laperception. La distinction des perceptions et des sensations est encore un grand résultat; et it est démontré aux yeux. Il y a deux moyens de faire perdre la vision par l'encéphale: 1° par les tubercules, c'est la perte du sens, de la sensation; 2° par les lobes, c'est la perte de la perception, de l'intelligence. La sensibilité n'est donc pas l'intelligence; penser n'est donc pas sentir; et voilà toute une philosophie renversée. L'idée n'est donc pas la sensation; et voilà encore une autre preuve du vice radical de cette philosophie." And again, p. 77, under the heading: Séparation de la Sensibilité et de la Perception:—"Il y a une de mesexpériencesqui sépare nettement lasensibilitéde laperception. Quand on enlève lecerveau proprement dit(lobesouhémisphères cérébraux) à un animal, l'animal perd la vue. Mais, par rapport a l'œil, rien n'est changé: les objets continuent à se peindre sur la rétine; l'irisreste contractile, lenerf optiquesensible, parfaitement sensible. Et cependantl'animal ne voit plus; il n'y a plusvision, quoique tout ce qui estsensationsubsiste; il n'y a plusvision, parce qu'il n'y a plusperception. Lepercevoir, et non lesentir, est donc le premier élément de l'intelligence. Laperceptionest partie de l'intelligence, car elle se perd avec l'intelligence, et par l'ablation du même organe, leslobesouhémisphères cérébraux; et lasensibilitén'en est point partie, puisqu'elle subsiste après la perte de l'intelligenceet l'ablation deslobesouhémisphères."The following famous verse of the ancient philosopher Epicharmus, proves that the ancients in general recognized the intellectual nature of perception: Νοῦςὁρῇκαὶ νοῦς ἀκούει· τἆλλα κωφὰ καὶ τυφλά. (Mens videt, mens audit; cætera surda et cœca.)[86]Plutarch in quoting this verse, adds:[87]ὡς τοῦ περὶ τὰ ὄμματα καὶ ὦτα πάθους, ἂν μὴ παρῇ τὸ φρονοῦν, αἴσθησιν οὐ ποιοῦντος (quia affectio oculorum et aurium nullum affert sensum, intelligentia absente). Shortly before too he says: Στράτωνος τοῦ φυσικοῦ λόγος ἐστίν, ἀποδεικνύων ὡς οὐδ' αἰσθάνεσθαι τοπαράπαν ἄνευ τοῦ νοεῖν ὑπάρχει. (Stratonis physici exstat ratiocinatio, qua "sine intelligentia sentiri omnino nihil posse" demonstrat.)[88]Again shortly after he says: ὅθεν ἀνάγκη, πᾶσιν, οἷς τὸ αἰσθάνεσθαι, καὶ τὸ νοεῖν ὑπάρχειν, εἰ τῷ νοεῖν αἰσθάνεσθαι πεφύκαμεν (quare necesse est, omnia, quæ sentiunt, etiam intelligere, siquidem intelligendo demum sentiamus).[89]A second verse of Epicharmus might be connected with this, which is quoted by Diogenes Laertes (iii. 16):Εὔμαιε, τὸ σοφόν ἐστιν οὐ καθ' ἓν μόνον,ἀλλ' ὅσα περ ζῇ, πάντα καὶ γνώμαν ἔχει.(Eumaee, sapientia non uni tantum competit, sed quæcunque vivunt etiam intellectum habent.) Porphyry likewise endeavours to show at length that all animals have understanding.[90]Now, that it should be so, follows necessarily from the intellectual character of perception. All animals, even down to the very lowest, must have Understanding—that is, knowledge of the causal law, although they have it in very different degrees of delicacy and of clearness; at any rate they must have as much of it as is required for perception by their senses; for sensation without Understanding would be not only a useless, but a cruel gift of Nature. No one, who has himself any intelligence, can doubt the existence of it in the higher animals. But at times it even becomes undeniably evident that their knowledge of causality is actuallyà priori, and that it does not arise from the habit of seeing one thing follow upon another. A very young puppy will not, for instance, jump off a table, because he foresees what would be the consequence. Not long ago I had some large curtains put up at my bed-room window, which reached down to the floor, and were drawn aside from the centre by means of a string. The first morning they were opened I was surprised to see my dog, a very intelligent poodle, standing quite perplexed, and looking upwards and sidewards for the cause of the phenomenon: that is, he was seeking for the change which he knewà priorimust have taken place. Next day the same thing happened again.—But even the lowest animals have perception—consequently Understanding—down to the aquatic polypus, which has no distinct organs of sensation, yet wanders from leaf to leaf on its waterplant, while clinging to it with its feelers, in search of more light.Nor is there, indeed, any difference, beyond that ofdegree, between this lowest Understanding and that of man, which we however distinctly separate from his Reason. The intermediate gradations are occupied by the various series of animals, among which the highest, such as the monkey, the elephant, the dog, astonish us often by their intelligence. But in every case the business of the Understanding is invariably to apprehend directly causal relations: first, as we have seen, those between our own body and other bodies, whence proceeds objective perception; then those between these objectively perceived bodies among themselves, and here, as has been shown in § 20, the causal relation manifests itself in three forms—as cause, as stimulus, and as motive. All movement in the world takes place according to these three forms of the causal relation, and through them alone does the intellect comprehend it. Now, if, of these three,causes, in the narrowest sense of the word, happen to be the object ofinvestigationfor the Understanding, it will produce Astronomy, Mechanics, Physics, Chemistry, and will invent machines for good and for evil; but in all cases a direct, intuitive apprehension of the causal connection will in the last resort lie at the bottom of all its discoveries. For the sole form and function of the Understanding is this apprehension, and not by any means the complicated machinery of Kant's twelve Categories, the nullity of which I have proved.—(All comprehension is a direct, consequently intuitive, apprehension of the causal connection; although this has to be reduced at once to abstract conceptions in order to be fixed. To calculate therefore, is not to understand, and, in itself, calculation conveys no comprehension of things. Calculation deals exclusively with abstract conceptions of magnitudes, whose mutual relations it determines. By it we never attain the slightest comprehension of a physical process, for this requiresintuitivecomprehension of space-relations, by means of which causes take effect.Calculations have merely practical, not theoretical, value. It may even be said thatwhere calculation begins, comprehension ceases; for a brain occupied with numbers is, as long as it calculates, entirely estranged from the causal connection in physical processes, being engrossed in purely abstract, numerical conceptions. The result, however, only shows ushow much, neverwhat. "L'expérience et le calcul," those watchwords of French physicists, are not therefore by any means adequate [for thorough insight].)—If, again,stimuliare the guides of the Understanding, it will produce Physiology of Plants and Animals, Therapeutics, and Toxicology. Finally, if it devotes itself to the study ofmotives, the Understanding will use them, on the one hand, theoretically, to guide it in producing works on Morality, Jurisprudence, History, Politics, and even Dramatic and Epic Poetry; on the other hand, practically, either merely to train animals, or for the higher purpose of making human beings dance to its music, when once it has succeeded in discovering which particular wire has to be pulled in order to move each puppet at its pleasure. Now, with reference to the function which effects this, it is quite immaterial whether the intellect turns gravitation ingeniously to account, and makes it serve its purpose by stepping in just at the right time, or whether it brings the collective or the individual propensities of men into play for its own ends. In its practical application we call the Understandingshrewdnessor, when used to outwit others,cunning; when its aims are very insignificant, it is calledslynessand, if combined with injury to others,craftiness. In its purely theoretical application, we call it simplyUnderstanding, the higher degrees of which are namedacumen,sagacity,discernment,penetration, while its lower degrees are termeddulness,stupidity,silliness, &c. &c. These widely differing degrees of sharpness are innate, and cannot be acquired; although, as I have already shown,even in the earliest stages of the application of the Understanding,i.e.in empirical perception, practice and knowledge of the material to which it is applied, are needed. Every simpleton has Reason—give him the premisses, and he will draw the conclusion; whereasprimary, consequently intuitive, knowledge is supplied by the Understanding: herein lies the difference. The pith of every great discovery, of every plan having universal historical importance, is accordingly the product of a happy moment in which, by a favourable coincidence of outer and inner circumstances, some complicated causal series, some hidden causes of phenomena which had been seen thousands of times before, or some obscure, untrodden paths, suddenly reveal themselves to the intellect.—By the preceding explanations of the processes in seeing and feeling, I have incontestably shown that empirical perception is essentially the work ofthe Understanding, for which the material only is supplied by the senses in sensation—and a poor material it is, on the whole; so thatthe Understandingis, in fact, the artist, while the senses are but the under-workmen who hand it the materials. But the process consists throughout in referring from given effects to their causes, which by this process are enabled to present themselves as objects in Space. The very fact that we presuppose Causality in this process, proves precisely that this law must have been supplied by the Understanding itself; for it could never have found its way into the intellect from outside. It is indeed the first condition of all empirical perception; but this again is the form in which all external experience presents itself to us; how then can this law of Causality be derived from experience, when it is itself essentially presupposed by experience?—It was just because of the utter impossibility of this, and because Locke's philosophy had put an end to allà priority, that Hume denied the whole reality of the conception ofCausality. He had besides already mentioned two false hypotheses in the seventh section of his "Inquiry concerning the Human Understanding," which recently have again been advanced: the one, that the effect of the will upon the members of our body; the other, that the resistance opposed to our pressure by outward objects, is the origin and prototype of the conception of Causality. Hume refutes both in his own way and according to his own order of ideas. I argue as follows. There is no causal connection whatever between acts of the will and actions of the body; on the contrary, both are immediately one and the same thing, only perceived in a double aspect—that is, on the one hand, in our self-consciousness, or inner sense, as acts of the will; on the other, simultaneously in exterior, spacial brain-perception, as actions of the body.[91]The second hypothesis is false, first because, as I have already shown at length, a mere sensation of touch does not yet give any objective perception whatever, let alone the conception of Causality, which never can arise from the feeling of an impeded muscular effort: besides impediments of this kind often occur without any external cause; secondly, because our pressing against an external object necessarily has a motive, and this already presupposes apprehension of that object, which again presupposes knowledge of Causality.—But the only means of radically proving the conception of Causality to be independent of all experience was by showing, as I have done, that the whole possibility of experience is conditioned by the conception of Causality. In § 23 I intend to show that Kant's proof, propounded with a similar intent, is false.This is also the proper place for drawing attention to thefact, that Kant either did not clearly recognise in empirical perception the mediation of the causal law—which law is known to us before all experience—or that he intentionally evaded mentioning it, because it did not suit his purpose. In the "Critique of Pure Reason," for instance, the relation between causality and perception is not treated in the "Doctrine of Elements," but in the chapter on the "Paralogisms of Pure Reason," where one would hardly expect to find it; moreover it appears in his "Critique of the Fourth Paralogism of Transcendental Psychology," and only in the first edition.[92]The very fact that this place should have been assigned to it, shows that in considering this relation, he always had the transition from the phenomenon to the thing in itself exclusively in view, but not the genesis of perception itself. Here accordingly he says that the existence of a real external object is not given directly in perception, but can be added to it in thought and thus inferred. In Kant's eyes, however, he who does this is a Transcendental Realist, and consequently on a wrong road. For by his "outward object" Kant here means the thing in itself. The Transcendental Idealist, on the contrary, stops short at the perception of something empirically real—that is, of something existing outside us in Space—without needing the inference of a cause to give it reality. Forperception, according to Kant, is quite directly accomplished without any assistance from the causal nexus, and consequently from the Understanding: he simply identifies perception with sensation. This we find confirmed in the passage which begins, "With reference to the reality of external objects, I need as little trust to inference," &c. &c.[93]and again in the sentence commencing with "Now we may welladmit," &c. &c.[94]It is quite clear from these passages that perception of external things in Space, according to Kant, precedes all application of the causal law, therefore that the causal law does not belong to perception as an element and condition of it: for him, mere sensation is identical with perception. Only in as far as we ask what may, in atranscendentalsense, existoutside of us: that is, when we ask for the thing in itself, is Causality mentioned as connected with perception. Moreover Kant admits the existence, nay, the mere possibility, of causality only in reflection: that is, in abstract, distinct knowledge by means of conceptions; therefore he has no suspicion that its application isanterior to all reflection, which is nevertheless evidently the case, especially in empirical, sensuous perception which, as I have proved irrefragably in the preceding analysis, could never take place otherwise. Kant is therefore obliged to leave the genesis of empirical perception unexplained. With him it is a mere matter of the senses, given as it were in a miraculous way: that is, it coincides with sensation. I should very much like my reflective readers to refer to the passages I have indicated in Kant's work, in order to convince themselves of the far greater accuracy of my view of the whole process and connection. Kant's extremely erroneous view has held its ground till now in philosophical literature, simply because no one ventured to attack it; therefore I have found it necessary to clear the way in order to throw light upon the mechanism of our knowledge.Kant's fundamental idealistic position loses nothing whatever, nay, it even gains by this rectification of mine, in as far as, with me, the necessity of the causal law is absorbed and extinguished in empirical perception as its product and cannot therefore be invoked in behalf of anentirely transcendent question as to the thing in itself. On referring to my theory above concerning empirical perception, we find that its first datum, sensation, is absolutely subjective, being a process within the organism, because it takes place beneath the skin. Locke has completely and exhaustively proved, that the feelings of our senses, even admitting them to be roused by external causes, cannot have any resemblance whatever to the qualities of those causes. Sugar, for instance, bears no resemblance at all to sweetness, nor a rose to redness. But that they should need an external cause at all, is based upon a law whose origin lies demonstrably within us, in our brain; therefore this necessity is not less subjective than the sensations themselves. Nay, evenTime—that primary condition of every possiblechange, therefore also of the change which first permits the application of the causal law—and not lessSpace—which alone renders the externalisation of causes possible, after which they present themselves to us as objects—even Time and Space, we say, are subjective forms of the intellect, as Kant has conclusively proved. Accordingly we find all the elements of empirical perception lying within us, and nothing contained in them which can give us reliable indications as to anything differing absolutely from ourselves, anything in itself.—But this is not all. What we think under the conceptionmatter, is the residue which remains over after bodies have been divested of their shape and of all their specific qualities: a residue, which precisely on that account must be identical in all bodies. Now these shapes and qualities which have been abstracted by us, are nothing but the peculiar, specially definedway in which these bodies act, which constitutes precisely their difference. If therefore we leave these shapes and qualities out of consideration, there remains nothing butmere activity in general, pure action as such, Causality itself, objectively thought—thatis, the reflection of our own Understanding, the externalised image of its sole function; and Matter is throughout pure Causality, its essence is Action in general.[95]This is why pure Matter cannot be perceived, but can only be thought: it is a something we add to every reality, as its basis, in thinking it. For pure Causality, mere action, without any defined mode of action, cannot become perceptible, therefore it cannot come within any experience.—Thus Matter is only the objective correlate to pure Understanding; for it is Causality in general, and nothing else: just as the Understanding itself is direct knowledge of cause and effect, and nothing else. Now this again is precisely why the law of causality is not applicable to Matter itself: that is to say, Matter has neither beginning nor end, but is and remains permanent. For as, on the one hand, Causality is the indispensable condition of all alternation in the accidents (forms and qualities) of Matter,i.e.of all passage in and out of being; but as, on the other hand, Matter is pure Causality itself, as such, objectively viewed: it is unable to exercise its own power upon itself, just as the eye can see everything but itself. "Substance" and Matter being moreover identical, we may callSubstance,actionviewedin abstracto:Accidents, particular modes of action, actionin concreto.—Now these are the results to which true,i.e.transcendental, Idealism leads. In my chief work I have shown that the thing in itself—i.e.whatever, on the whole, exists independently of our representation—cannot be got at by way of representation, but that, to reach it, we must follow quite a different path, leading through the inside of things, which lets us into the citadel, as it were, by treachery.—But it would be downright chicanery, nothing else, totry and compare, let alone identify, such an honest, deep, thorough analysis of empirical perception as the one I have just given, which proves all the elements of perception to be subjective, with Fichte's algebraic equations of theEgoand theNon-Ego; with his sophistical pseudo-demonstrations, which in order to be able to deceive his readers had to be clothed in the obscure, not to say absurd, language adopted by him; with his explanations of the way in which theEgospins theNon-Egoout of itself; in short, with all the buffoonery of scientific emptiness.[96]Besides, I protest altogether against any community with this Fichte, as Kant publicly and emphatically did in a noticead hocin the "Jenaer Litteratur Zeitung."[97]Hegelians and similar ignoramuses may continue to hold forth to their heart's content upon Kant-Fichteian philosophy: there exists a Kantian philosophy and a Fichteian hocus-pocus,—this is the true state of the case, and will remain so, in spite of those who delight in extolling what is bad and in decrying what is good, and of these Germany possesses a larger number than any other country.§ 22.Of the Immediate Object.Thus it is from the sensations of our body that we receive the data for the very first application of the causal law, and it is precisely by that application that the perception of this class of objects arises. They therefore have their essence and existence solely in virtue of the intellectual function thus coming into play, and of its exercise.Now, as far as it is the starting-point,i.e.the mediator, for our perception of all other objects, I have called the bodily organism, in the first edition of the present work, theImmediate Object; this, however, must not be taken in a strictly literal sense. For although our bodily sensations are all apprehended directly, still this immediate apprehension does not yet make our body itself perceptible to us as an object; on the contrary, up to this point all remains subjective, that is to say, sensation. From this sensation certainly proceeds the perception of all other objects as the causes of such sensations, and these causes then present themselves to us as objects; but it is not so with the body itself, which only supplies sensations to consciousness. It is onlyindirectlythat we know even this body objectively,i.e.as an object, by its presenting itself, like all other objects, as the recognised cause of a subjectively given effect—and precisely on this accountobjectively—in our Understanding, or brain (which is the same). Now this can only take place when its own senses are acted upon by its parts: for instance, when the body is seen by the eye, or felt by the hand, &c., upon which data the brain (or understanding) forthwith constructs it as to shape and quality in space.—The immediate presence in our consciousness of representations belonging to this class, depends therefore upon the position assigned to them in the causal chain—by which all things areconnected—relatively to the body (for the time being) of the Subject—by which (the Subject) all things areknown.§ 23.Arguments against Kant's Proof of theà priorityof the conception of Causality.One of the chief objects of the "Critique of Pure Reason" is to show the universal validity, for all experience, of the causal law, itsà priority, and, as a necessaryconsequence of this, its restriction to possible experience. Nevertheless, I cannot assent to the proof there given of theà priorityof the principle, which is substantially this:—"Thesynthesisof the manifold by the imagination, which is necessary for all empirical knowledge, gives succession, but not yet determinate succession: that is, it leaves undetermined which of two states perceived was the first, not only in my imagination, but in the object itself. But definite order in this succession—through which alone what we perceive becomes experience, or, in other words, authorizes us to form objectively valid judgments—is first brought into it by the purely intellectual conception of cause and effect. Thus the principle of causal relation is the condition which renders experience possible, and, as such, it is given usà priori."[98]According to this, the order in which changes succeed each other in real objects becomes known to us as objective only by their causality. This assertion Kant repeats and explains in the "Critique of Pure Reason," especially in his "Second Analogy of Experience,"[99]and again at the conclusion of his "Third Analogy," and I request every one who desires to understand what I am now about to say, to read these passages. In them he affirms everywhere thatthe objectivity of the succession of representations—which he defines as their correspondence with the succession of real objects—is only known through the rule by which they follow upon one another: that is, through the law of causality; that my mere apprehension consequently leaves the objective relation between phenomena following one another quite undetermined: sinceI merely apprehend the succession of my own representations, but the succession in my apprehension does not authorize me to form any judgment whatever as to the succession in the object, unless that judgment be based upon causality; and since, besides, I might invert the order in which these perceptions follow each other in my apprehension, there being nothing which determines them as objective. To illustrate this assertion, Kant brings forward the instance of a house, whose parts we may consider in any order we like, from top to bottom, or from bottom to top; the determination of succession being in this case purely subjective and not founded upon an object, because it depends upon our pleasure. In opposition to this instance, he brings forward the perception of a ship sailing down a river, which we see successively lower and lower down the stream, which perception of the successively varying positions of the ship cannot be changed by the looker-on. In this latter case, therefore, he derives the subjective following in his own apprehension from the objective following in the phenomenon, and on this account he calls it anevent. Now I maintain, on the contrary, thatthere is no difference at all between these two cases, that both are events, and that our knowledge of both is objective: that is to say, it is knowledge of changes in real objects recognized as such by the Subject.Both are changes of relative position in two bodies.In the first case, one of these bodies is a part of the observer's own organism, the eye, and the other is the house, with respect to the different parts of which the eye successively alters its position. In the second, it is the ship which alters its position towards the stream; therefore the change occurs between two bodies. Both are events, the only difference being that, in the first, the change has its starting-point in the observer's own body, from whose sensations undoubtedly all his perceptions originally proceed, but which is nevertheless an objectamong objects, and in consequence obeys the laws of the objective, material world. For the observer, as a purely cognising individual, any movement of his body is simply an empirically perceived fact. It would be just as possible in the second as in the first instance, to invert the order of succession in the change, were it as easy for the observer to move the ship up the stream as to alter the direction of his own eyes. For Kant infers the successive perception of different parts of the house to be neither objective nor an event, because it depends upon his own will. But the movement of his eyes in the direction from roof to basement is one event, and in the direction from basement to roof another event, just as much as the sailing of the ship. There is no difference whatever here, nor is there any difference either, as to their being or not being events, between my passing a troop of soldiers and their passing me. If we fix our eyes on a ship sailing close by the shore on which we are standing, it soon seems as if it were the ship that stood still and the shore that moved. Now, in this instance we are mistaken, it is true, as to the cause of the relative change of position, since we attribute it to a wrong cause; the real succession in the relative positions of our body towards the ship is nevertheless quite rightly and objectively recognised by us. Even Kant himself would not have believed that there was any difference, had he borne in mind that his own body was an object among objects, and that the succession in his empirical perceptions depended upon the succession of the impressions received from other objects by his body, and was therefore an objective succession: that is to say, one which takes place among objectsdirectly(if not indirectly) and independently of the will of the Subject, and which may therefore be quite well recognised without any causal connection between the objects acting successively on his body.Kant says, Time cannot be perceived; therefore no succession of representations can be empirically perceived as objective:i.e.can be distinguished as changes in phenomena from the changes of mere subjective representations. The causal law, being a rule according to which states follow one another, is the only means by which the objectivity of a change can be known. Now, the result of his assertion would be, that no succession in Time could be perceived by us as objective, excepting that of cause and effect, and that every other succession of phenomena we perceive, would only be determined so, and not otherwise, by our own will. In contradiction to all this I must adduce the fact, that it is quite possible for phenomena tofollow uponone another withoutfollowing fromone another. Nor is the law of causality by any means prejudiced by this; for it remains certain that each change is the effect of another change, this being firmly establishedà priori; only each change not only follows upon the single one which is its cause, but upon all the other changes which occur simultaneously with that cause, and with which that cause stands in no causal connection whatever. It is not perceived by me exactly in the regular order of causal succession, but in quite a different order, which is, however, no less objective on that account, and which differs widely from any subjective succession depending on my caprice, such as, for instance, the pictures of my imagination. The succession, in Time, of events which stand in no causal connection with each other is precisely what we callcontingency.[100]Just as I am leaving my house, a tile happens to fall from the roof which strikes me; now, there is no causal connection whatever between my going out andthe falling of the tile; yet the order of their succession—that is, that my going out preceded the falling of the tile—is objectively determined in my apprehension, not subjectively by my will, by which that order would otherwise have most likely been inverted. The order in which tones follow each other in a musical composition is likewise objectively determined, not subjectively by me, the listener; yet who would think of asserting that musical tones follow one another according to the law of cause and effect? Even the succession of day and night is undoubtedly known to us as an objective one, but we as certainly do not look upon them as causes and effects of one another; and as to their common cause, the whole world was in error till Copernicus came; yet the correct knowledge of their succession was not in the least disturbed by that error. Hume's hypothesis, by the way, also finds its refutation through this; since the following of day and night upon each other—the most ancient of all successions and the one least liable to exception—has never yet misled anyone into taking them for cause and effect of each other.
The first thing it does is to set right the impression of the object, which is produced on the retina upside down. That original inversion is, as we know, brought about in the following manner. As each point of the visible objectsends forth its rays towards all sides in a rectilinear direction, the rays from its upper extremity cross those from its lower extremity in the narrow aperture of the pupil, by which the former impinge upon the bottom, the latter upon the top, those projected from the right side upon the left, andvice versa. The refracting apparatus of the eye, which consists of thehumor aqueus,lens,et corpus vitreum, only serves to concentrate the rays of light proceeding from the object, so as to find room for them on the small space of the retina. Now, if seeing consisted in mere sensation, we should perceive the impression of the object turned upside down, because we receive it thus; but in that case we should perceive it as something within our eye, for we should stop short at the sensation. In reality, however, the Understanding steps in at once with its causal law, and as it has received from sensation the datum of the direction in which the ray impinged upon the retina, it pursues that direction retrogressively up to the cause on both lines; so that this time the crossing takes place in the opposite direction, and the cause presents itself upright as an external object in Space,i.e.in the position in which it originally sent forth its rays, not that in which they reached the retina (see fig. 1).—The purely intellectual nature of this process, to the exclusion of all other, more especially of physiological, explanations, may also be confirmed by thefact, that if we put our heads between our legs, or lie down on a hill head downwards, we nevertheless see objects in their right position, and not upside down; although the portion of the retina, which is usually met by the lower part of the object is then met by the upper: in fact, everything is topsy turvy excepting the Understanding.
rays entering the retina of the eyeFig. 1.
Fig. 1.
Thesecondthing which the Understanding does in converting sensation into perception, is to make a single perception out of a double sensation; for each eye in fact receives its own separate impression from the object we are looking at; each even in a slightly different direction: nevertheless that object presents itself as a single one. This can only take place in the Understanding, and the process by which it is brought about is the following: Our eyes are never quite parallel, excepting when we look at a distant object,i.e.one which is more than 200 feet from us. At other times they are both directed towards the object we are viewing, whereby they converge, so as to make the lines proceeding from each eye to the exact point of the object on which it is fixed, form anangle, called theoptic angle; the lines themselves are calledoptic axes. Now, when the object lies straight before us, these lines exactly impinge upon the centre of each retina, therefore in two points which correspond exactly to each other in each eye. The Understanding, whose only business it is to look for thecauseof all things, at once recognises the impression as coming from asingleoutside point, although here the sensation is double, and attributes it toonecause, which therefore presents itself as a single object. For all that is perceived by us, is perceived as acause—that is to say, as the cause of an effect we have experienced, consequentlyin the Understanding. As, nevertheless, we take in not only a single point, but a considerable surface of the object with both eyes, and yet perceive it as a single object, it will be necessary to pursue thisexplanation still further. All those parts of the object which lie to one side of the vertex of the optic angle no longer send their rays straight into the centre, but to the side, of the retina in each eye; in both sides, however, to the same, let us say the left, side. The points therefore upon which these rays impinge,correspond symmetrically to each other, as well as the centres—in other words, they arehomonymous points. The Understanding soon learns to know them, and accordingly extends the above-mentioned rule of its causal perception to them also; consequently it not only refers those rays which impinge upon the centre of each retina, but those also which impinge upon all the other symmetrically corresponding places in both retinas, to a single radiant point in the object viewed: that is, it sees all these points likewise as single, and the entireobject also. Now, it should be well observed, that in this process it is not the outer side of one retina which corresponds to the outer side of the other, and the inner to the inner of each, but the right side of one retina which corresponds to the right side of the other, and so forth; so that this symmetrical correspondence must not be taken in a physiological, but in a geometrical sense. Numerous and very clear illustrations of this process, and of all the phenomena which are connected with it, are to be found in Robert Smith's "Optics," and partly also in Kästner's German translation (1755). I only giveone(fig. 2), which, properly speaking, represents a special case, mentioned further on, but which may also serve to illustrate the whole, if we leave the point R out of question. According to this illustration, we invariably direct both eyes equally towards the object, in order that the symmetrically corresponding places on both retinas may catch the rays projected from the same points. Now, when we move our eyes upwards and downwards, to the sides, and in all directions, the point in the object which first impinged upon the central point of each retina, strikes a different place every time, but in all cases one which, in each eye, corresponds to the place bearing the same name in the other eye. In examining (perlustrare) an object, we let our eyes glide backwards and forwards over it, in order to bring each point of it successively into contact with the centre of the retina, which sees most distinctly: we feel it all over with our eyes. It is therefore obvious that seeing singly with two eyes is in fact the same process as feeling a body with ten fingers, each of which receives a different impression, each moreover in a different direction: the totality of these impressions being nevertheless recognised by the Understanding as proceeding fromoneobject, whose shape and size it accordingly apprehends and constructs in Space. This is why it is possible for a blind man to becomea sculptor, as was the case, for instance, with the famous Joseph Kleinhaus, who died in Tyrol, 1853, having been a sculptor from his fifth year.[80]For, no matter from what cause it may have derived its data, perception is invariably an operation of the Understanding.
the symmetry of the raysFig. 2.
Fig. 2.
But just as a single ball seems to me double, if I touch it with my fingers crossed—since my Understanding, at once reverting to the cause and constructing it according to the laws of Space, takes for granted that the fingers are in their normal position and of course cannot do otherwise than attribute two spherical surfaces, which come in contact with the outer sides of the first and middle fingers, to two different balls—just so also does an object seem double, if my eyes, instead of converging symmetrically and enclosing the optic angle at a single point of the object, each view it at a different inclination—in other words, if I squint. For the rays, which in this case emanate from one point of the object, no longer impinge upon those symmetrically corresponding points in both retinas with which my mind has grown familiar by long experience, but upon other, quite different ones which, in a symmetrical position of the eyes, could only be affected in this way by differentbodies; I therefore now seetwoobjects, precisely because perception takes place by means of, and within, the Understanding.—The same thing happens without squinting when, for instance, I look fixedly at the furthest of two objects placed at unequal distances before me, and complete the optic angle at it; for then the rays emanating from the nearer object do not impinge upon symmetrically corresponding places in both retinas, wherefore my Understanding attributes them to two objects,i.e.I see the nearer object double (see fig. 2, page 70). If, on the contrary, I complete the optic angle at the nearer object, by looking steadily at it, the further object appears double. It is easy to test this by holding a pencil two feet from the eyes, and looking alternately at it and at some other more distant object behind it.
But the finest thing of all is, that this experiment may quite well be reversed: so that, with two real objects straight before and close to us, and with our eyes wide open, we nevertheless see butone. This is the most striking proof that perception is a work of the Understanding and by no means contained in sensation. Let two cardboard tubes, about 8 inches long and 1-1/2 inches in diameter, be fastened parallel to one another, like those of a binocular telescope, and fix a shilling at the end of each tube. On applying our eyes to the opposite extremity and looking through the tubes, we shall see onlyoneshilling surrounded byonetube. For in this case the eyes being forced into a completely parallel position, the rays emanating from the coins impinge exactly upon the centres of the two retinas and those points which immediately surround them, therefore upon places which correspond symmetrically to each other; consequently the Understanding, taking for granted the usual convergent position of the optic axes when objects are near, admits but one object as the cause of the reflected rays. In other words, we see butone object; so direct is the act of causal apprehension in the Understanding.
We have not space enough here to refute one by one the physiological explanations of single vision which have been attempted; but their fallacy is shown by the following considerations:—
1o. If seeing single were dependent upon an organic connection, the corresponding points in both retinas, on which this phenomenon is shown to depend, would correspondorganically, whereas they do so in a merelygeometricalsense, as has already been said. For, organically speaking, the two inner and two outer corners of the eyes are those which correspond, and so it is with the other parts also; whereas for the purpose of single vision, it is the right side of the right retina which corresponds to the right side of the left retina, and so on, as the phenomena just described irrefutably show. It is also precisely on account of the intellectual character of the process, that only the most intelligent animals, such as the higher mammalia and birds of prey—more especially owls—have their eyes placed so as to enable them to direct both optic axes to the same point.
2o. The hypothesis of a confluence or partial intersection of the optic nerves before entering the brain, originated by Newton,[81]is false, simply because it would then be impossible to see double by squinting. Vesalius and Cæsalpinus besides have already brought forward anatomical instances in which subjects saw single, although neither fusion nor even contact of the optic nerves had taken place. A final argument against the hypothesis of a mixed impression is supplied by the fact, that on closing our right eye firmly and looking at the sun with our left, the bright image which persists for a time is always in the left, never in the right, eye: andvice versa.
Thethirdprocess by which the Understanding converts sensation into perception, consists in constructing bodies out of the simple surfaces hitherto obtained—that is, in adding the third dimension. This it does by estimating the expansion of bodies in this third dimension in Space—which is known to the Understandingà priori—through Causality, according to the degree in which the eye is affected by the objects, and to the gradations of light and shade. In fact, although objects fill Space in all three dimensions, they can only produce an impression upon the eye with two; for the nature of that organ is such, that our sensation, in seeing, is merely planimetrical, not stereometrical. All that is stereometrical in our perception is added by the Understanding, which has for its sole data the direction whence the eye receives its impression, the limits of that impression, and the various gradations of light and dark: these data directly indicate their causes, and enable us to distinguish whether what we have before us is a disk or a ball. This mental process, like the preceding ones, takes place so immediately and with such rapidity, that we are conscious of nothing but the result. It is this which makes perspective drawing so difficult a problem, that it can only be solved by mathematics and has to be learnt; although all it has to do, is to represent the sensation of seeing as it presents itself to our Understanding as a datum for the third process: that is, visual sensation in its merely planimetrical extension, to thetwodimensions of which extension, together with the said data in them, the Understanding forthwith adds thethird, in contemplating a drawing as well as in contemplating reality. Perspective drawing is, in fact, a sort of writing which can be read as easily as printed type, but which few are able to write; precisely because our intellect, in perceiving, only apprehends effects with a view to constructing their causes, immediately losing sight of the former as soon as it hasdiscovered the latter. For instance, we instantly recognise a chair, whatever position it may be in; while drawing a chair in any position belongs to the art which abstracts from this third process of the Understanding, in order to present the data alone for the spectator himself to complete. In its narrowest acceptation, as we have already seen, this is the art of drawing in perspective; in a more comprehensive sense, it is the whole art of painting. A painting presents us with outlines drawn according to the rules of perspective; lighter and darker places proportioned to the effect of light and shade; finally patches of colouring, which are determined as to quality and intensity by the teaching of experience. This the spectator reads and interprets by referring similar effects to their accustomed causes. The painter's art consists in consciously retaining the data of visual sensation in the artist's memory, as they arebeforethis third intellectual process; while we, who are not artists, cast them aside without retaining them in our memory, as soon as we have made use of them for the purpose described above. We shall become still better acquainted with this third intellectual process by now passing on to a fourth, which, from its intimate connection with the third, serves to elucidate it.
Thisfourthoperation of the Understanding consists in acquiring knowledge of the distance of objects from us: it is this precisely which constitutes that third dimension of which we have been speaking. Visual sensation, as we have said, gives us thedirectionin which objects lie, but not theirdistancefrom us: that is, not theirposition. It is for theUnderstandingtherefore to find out this distance; or, in other words, the distance must be inferred from purelycausaldeterminations. Now the most important of these is thevisual angle, which objects subtend; yet even this is quite ambiguous and unable to decide anything by itself. It is like a word of double meaning:the sense, in which it is to be understood, can only be gathered from its connection with the rest. An object subtending the same visual angle may in fact be small and near, or large and far off; and it is only when we have previously ascertained its size, that the visual angle enables us to recognise its distance: and conversely, its size, when its distance is known to us. Linear perspective is based upon the fact that the visual angle diminishes as the distance increases, and its principles may here be easily deduced. As our sight ranges equally in all directions, we see everything in reality as from the interior of a hollow sphere, of which our eye occupies the centre. Now in the first place, an infinite number of intersecting circles pass through the centre of this sphere in all directions, and the angles measured by the divisions of these circles are the possible angles of vision. In the second place, the sphere itself modifies its size according to the length of radius we give to it; therefore we may also imagine it as consisting of an infinity of concentric, transparent spheres. As all radii diverge, these concentric spheres augment in size in proportion to their distance from us, and the degrees of their sectional circles increase correspondingly: therefore the true size of the objects which occupy them likewise increases. Thus objects are larger or smaller according to the size of the spheres of which they occupy similar portions—say 10°—while their visual angle remains unchanged in both cases, leaving it therefore undecided, whether the 10° occupied by a given object belong to a sphere of 2 miles, or of 10 feet diameter. Conversely, if the size of the object has been ascertained, the number of degrees occupied by it will diminish in proportion to the distance and the size of the sphere to which we refer it, and all its outlines will contract in similar proportion. From this ensues the fundamental law of all perspective; for, as objects and the intervals between them must necessarilydiminish in constant proportion to their distance from us, all their outlines thereby contracting, the result will be, that with increasing distance, what is above us will descend, what is below us will ascend, and all that lies at our sides will come nearer together. This progressive convergence, this linear perspective, no doubt enables us to estimate distances, so far as we have before us an uninterrupted succession of visibly connected objects; but we are not able to do this by means of the visual angle alone, for here the help of another datum is required by the Understanding, to act, in a sense, as commentary to the visual angle, by indicating more precisely the share we are to attribute to distance in that angle. Now there are four principal data of this kind, which I am about to specify. Thanks to these data, even where there is no linear perspective to guide us, if a man standing at a distance of 200 feet appears to me subtending a visual angle twenty-four times smaller than if he were only 2 feet off, I can nevertheless in most cases estimate his size correctly. All this proves once more that perception is not only a thing of the senses, but of the intellect also.—I will here add the following special and interesting fact in corroboration of what I have said about the basis of linear perspective as well as about the intellectual nature of all perception. When I have looked steadily at a coloured object with sharply defined outlines—say a red cross—long enough for the physiological image to form in my eye as a green cross, the further the surface on to which I project it, the larger it will appear to me: andvice versa. For the image itself occupies an unvarying portion of my retina,i.e.the portion originally affected by the red cross; therefore when referred outwards, or, in other words, recognised as the effect of an external object, it forms an unchanging visual angle, say of 2°. Now if, in this case, where all commentary to the visual angle is wanting, I remove it toa distant surface, with which I necessarily identify it as belonging to its effect, the cross will occupy 2° of a distant and therefore larger sphere, and is consequently large. If, on the other hand, I project the image on to a nearer object, it will occupy 2° of a smaller sphere, and is therefore small. The resulting perception is in both cases completely objective, quite like that of an external object; and as it proceeds from an entirely subjective reason (from the image having been excited in quite a different way), it thus confirms the intellectual character of all objective perception.—This phenomenon (which I distinctly remember to have been the first to notice, in 1815) forms the theme of an essay by Séguin, published in the "Comptes rendus" of the 2nd August, 1858, where it is served up as a new discovery, all sorts of absurd and distorted explanations of it being given.Messieurs les illustres confrèreslet pass no opportunity for heaping experiment upon experiment, the more complicated the better.Expérience!is their watchword; yet how rarely do we meet with any sound, genuine reflection upon the phenomena observed!Expérience! expérience!followed by twaddle.
To return to the subsidiary data which act as commentaries to a given visual angle, we find foremost among them themutationes oculi internæ, by means of which the eye adapts its refractory apparatus to various distances by increasing and diminishing the refraction. In what these modifications consist, has not yet been clearly ascertained. They have been sought in the increased convexity, now of thecornea, now of the crystallinelens; but the latest theory seems to me the most probable one, according to which the lens is moved backwards for distant vision and forwards for near vision, lateral pressure, in the latter case, giving it increased protuberance; so that the process would exactly resemble the mechanism of an opera-glass.Kepler, however, had, in the main, already expressed this theory, which may be found explained in A. Hueck's pamphlet, "Die Bewegung der Krystallinse," 1841. If we are not clearly conscious of these inner modifications of the eye, we have at any rate a certain feeling of them, and of this we immediately avail ourselves to estimate distances. As however these modifications are not available for the purposes of clear sight beyond the range of from about 7 inches to 16 feet, the Understanding is only able to apply this datum within those limits.
Beyond them, however, the second datum becomes available: that is to say, theoptic angle, formed by the two optic axes, which we had occasion to explain when speaking of single vision. It is obvious that this optic angle becomes smaller, the further the object is removed: andvice versa. This different direction of the eyes, with respect to each other, does not take place without producing a slight sensation, of which we are nevertheless only in so far conscious as the Understanding makes use of it, as a datum, in estimating distances intuitively. By this datum we are not only enabled to cognize the distance, but the precise position of the object viewed, by means of the parallax of the eyes, which consists in each eye seeing the object in a slightly different direction; so that if we close one eye, the object seems to move. Thus it is not easy to snuff a candle with one eye shut, because this datum is then wanting. But as the direction of the eyes becomes parallel as soon as the distance of the object reaches or exceeds 200 feet, and as the optic angle consequently then ceases to exist, this datum only holds good within the said distance.
Beyond it, the Understanding has recourse toatmospheric perspective, which indicates a greater distance by means of the increasing dimness of all colours, of the appearance of physical blue in front of all dark objects(according to Göthe's perfectly correct and true theory of colours), and also of the growing indistinctness of all outlines. In Italy, where the atmosphere is very transparent, this datum loses its power and is apt to mislead: Tivoli, for instance, seems to be very near when seen from Frascati. On the other hand, all objects appear larger in a mist, which is an abnormal exaggeration of the datum; because our Understanding assumes them to be further from us.
Finally, there remains the estimation of distance by means of the size (known to us intuitively) of intervening objects, such as fields, woods, rivers, &c. &c. This mode of estimation is only applicable where there is uninterrupted succession: in other words, it can only be applied to terrestrial, not to celestial objects. Moreover, we have in general more practice in using it horizontally than vertically: a ball on the top of a tower 200 feet high appears much smaller to us than when lying on the ground 200 feet from us; because, in the latter case, we estimate the distance more accurately. When we see human beings in such a way, that what lies between them and ourselves is in a great measure hidden from our sight, they always appear strikingly small.
The fact that our Understanding assumes everything it perceives in a horizontal direction to be farther off, therefore larger, than what is seen in a vertical direction, must partly be attributed to this last mode of estimating distances, inasmuch as it only holds good when applied horizontally and to terrestrial objects; but partly also to our estimation of distances by atmospheric perspective, which is subject to similar conditions. This is why the moon seems so much larger on the horizon than at its zenith, although its visual angle accurately measured—that is, the image projected by it on to the eye—is not at all larger in one case than in the other; and this also accounts for the flattened appearance ofthe vault of the sky: that is to say, for its appearing to have greater horizontal than vertical extension. Both phenomena therefore are purely intellectual or cerebral, not optical. If it be objected, that even when at its zenith, the moon occasionally has a hazy appearance without seeming to be larger, we answer, that neither does it in that case appear red; for its haziness proceeds from a greater density of vapours, and is therefore of a different kind from that which proceeds from atmospheric perspective. To this may be added what I have already said: that we only apply this mode of estimating distances in a horizontal, not in a perpendicular, direction; besides, in this case, other correctives come into play. It is related of Saussure that, when on the Mont Blanc, he saw so enormous a moon rise, that, not recognising what it was, he fainted with terror.
The properties of the telescope and magnifying glass, on the other hand, depend upon a separate estimate according to the visual angle alone:i.e., that of size by distance, and of distance by size; because here the four other supplementary means of estimating distances are excluded. The telescope in reality magnifies objects, while it only seems to bring them nearer; because their size being known to us empirically, we here account for its apparent increase by a diminution of their distance from us. A house seen through a telescope, for instance, seems to be ten times nearer, not ten times larger, than seen with the naked eye. The magnifying glass, on the contrary, does not really magnify, but merely enables us to bring the object nearer to our eyes than would otherwise be possible; so that it only appears as large as it would at that distance even without the magnifying glass. In fact, we are prevented from seeing objects distinctly at less than from eight to ten inches' distance from our eyes, by the insufficient convexity of the ocularlens and cornea; but if we increase the refraction by substituting the convexity of the magnifying glass for that of the lens and cornea, we then obtain a clear image of objects even when they are as near as half an inch from our eyes. Objects thus seen in close proximity to us and in the size corresponding to that proximity, are transferred by our Understanding to the distance at which we naturally see distinctly,i.e.to about eight or ten inches from our eyes, and we then estimate their magnitude according to this distance and to the given visual angle.
I have entered thus fully into detail concerning all the different processes by which seeing is accomplished, in order to show clearly and irrefragably that the predominant factor in them isthe Understanding, which, by conceiving each change as aneffectand referring that effect to itscause, produces the cerebral phenomenon of the objective world on the basis of theà priorifundamental intuitions of Space and Time, for which it receives merely a few data from the senses. And moreover the Understanding effects this exclusively by means of its own peculiar form, the law of Causality; therefore quite directly and intuitively, without any assistance whatever from reflection—that is, from abstract knowledge by means of conceptions and of language, which are the materials ofsecondaryknowledge,i.e.ofthought, therefore ofReason.
That this knowledge through the Understanding is independent of Reason's assistance, is shown even by the fact, that when, at any time, the Understanding attributes a given effect to a wrong cause, actually perceiving that cause, wherebyillusionarises, our Reason, however clearly it may recognisein abstractothe true state of the matter, is nevertheless unable to assist the Understanding, and the illusion persists undisturbed in spite of that better knowledge. The above-mentioned phenomena of seeing and feeling double, which result from an abnormal positionof the organs of touch and sight, are instances of such illusions; likewise the apparently increased size of the rising moon; the image which forms in the focus of a concave mirror and exactly resembles a solid body floating in space; the painted relievo which we take for real; the apparent motion of a shore or bridge on which we are standing, if a ship happens to pass along or beneath it; the seeming proximity of very lofty mountains, owing to the absence of atmospheric perspective, which is the result of the purity of the air round their summits. In these and in a multitude of similar cases, our Understanding takes for granted the existence of the usual cause with which it is conversant and forthwith perceives it, though our Reason has arrived at the truth by a different road; for, the knowledge of the Understanding being anterior to that of the Reason, the intellect remains inaccessible to the teaching of the Reason, and thus theillusion—that is, the deception of the Understanding—remains immovable; albeiterror—that is, the deception of the Reason—is obviated.—That which is correctly known by the Understanding isreality: that which is correctly known by the Reason istruth, or in other terms, a judgment having a sufficient reason;illusion(that which is wrongly perceived) we oppose toreality:error(that which is wrongly thought) totruth.
The purely formal part of empirical perception—that is, Space, Time, and the law of Causality—is containedà prioriin the intellect; but this is not the case with the application of this formal part to empirical data, which has to be acquired by the Understanding through practice and experience. Therefore new-born infants, though they no doubt receive impressions of light and of colour, still do not apprehend or indeed, strictly speaking, see objects. The first weeks of their existence are rather passed in a kind of stupor, from which they awaken by degrees when their Understanding begins to apply its function to thedata supplied by the senses, especially those of touch and of sight, whereby they gradually gain consciousness of the objective world. This newly-arising consciousness may be clearly recognised by the look of growing intelligence in their eyes and a degree of intention in their movements, especially in the smile with which they show for the first time recognition of those who take care of them. They may even be observed to make experiments for a time with their sight and touch, in order to complete their apprehension of objects by different lights, in different directions and at different distances: thus pursuing a silent, but serious course of study, till they have succeeded in mastering all the intellectual operations in seeing which have been described. The fact of this schooling can be ascertained still more clearly through those who, being born blind, have been operated upon late in life, since they are able to give an account of their impressions. Cheselden's blind man[82]was not an isolated instance, and we find in all similar cases the fact corroborated, that those who obtain their sight late in life, no doubt, see light, outlines, and colours, as soon as the operation is over, but that they have no objective perception of objects until their Understanding has learnt to apply its causal law to data and to changes which are new to it. On first beholding his room and the various objects in it, Cheselden's blind man did not distinguish one thing from another; he simply received the general impression of a totality all in one piece, which he took for a smooth, variegated surface. It never occurred to him to recognise a number of detached objects, lying one behind the other at different distances. With blind people of this sort, it is by the sense of touch, to which objects are already known, that they have to be introduced to the sense ofsight. In the beginning, the patient has no appreciation whatever of distances and tries to lay hold of everything. One, when he first saw his own house from outside, could not conceive how so small a thing could contain so many rooms. Another was highly delighted to find, some weeks after the operation, that the engravings hanging on the walls of his room represented a variety of objects. The "Morgenblatt" of October 23rd, 1817, contains an account of a youth who was born blind, and obtained his sight at the age of seventeen. He had to learn intelligent perception, for at first sight he did not even recognise objects previously known to him through the sense of touch. Every object had to be introduced to the sense of sight by means of the sense of touch. As for the distances of the objects he saw, he had no appreciation whatever of them, and tried to lay hold indiscriminately of everything, far or near.—Franz expresses himself as follows:[83]—
"A definite idea of distance, as well as of form and size, is only obtained by sight and touch, and by reflecting on the impressions made on both senses; but for this purpose we must take into account the muscular motion and voluntary locomotion of the individual.—Caspar Hauser, in a detailed account of his own experience in this respect, states, that upon his first liberation from confinement, whenever he looked through the window upon external objects, such as the street, garden, &c., it appeared to him as if there were a shutter quite close to his eye, and covered with confused colours of all kinds, in which he could recognise or distinguish nothing singly. He says farther, that he did not convince himself till after some time during his walks out of doors, that what had at first appeared to him as a shutter of various colours, as well as many other objects, were in reality very different things; and that at length the shutter disappeared, and he saw and recognised all things in their just proportions. Persons born blind who obtain their sight by an operation in later years only, sometimes imagine that all objects touch their eyes, and lie so near to them that they are afraid of stumbling against them; sometimes they leap towards the moon, supposing that they canlay hold of it; at other times they run after the clouds moving along the sky, in order to catch them, or commit other such extravagancies. Since ideas are gained by reflection upon sensation, it is further necessary in all cases, in order that an accurate idea of objects may be formed from the sense of sight, that the powers of the mind should be unimpaired, and undisturbed in their exercise. A proof of this is afforded in the instance related by Haslam,[84]of a boy who had no defect of sight, but was weak in understanding, and who in his seventh year was unable to estimate the distances of objects, especially as to height; he would extend his hand frequently towards a nail on the ceiling, or towards the moon, to catch it. It is therefore the judgment which corrects and makes clear this idea, or perception of visible objects."
"A definite idea of distance, as well as of form and size, is only obtained by sight and touch, and by reflecting on the impressions made on both senses; but for this purpose we must take into account the muscular motion and voluntary locomotion of the individual.—Caspar Hauser, in a detailed account of his own experience in this respect, states, that upon his first liberation from confinement, whenever he looked through the window upon external objects, such as the street, garden, &c., it appeared to him as if there were a shutter quite close to his eye, and covered with confused colours of all kinds, in which he could recognise or distinguish nothing singly. He says farther, that he did not convince himself till after some time during his walks out of doors, that what had at first appeared to him as a shutter of various colours, as well as many other objects, were in reality very different things; and that at length the shutter disappeared, and he saw and recognised all things in their just proportions. Persons born blind who obtain their sight by an operation in later years only, sometimes imagine that all objects touch their eyes, and lie so near to them that they are afraid of stumbling against them; sometimes they leap towards the moon, supposing that they canlay hold of it; at other times they run after the clouds moving along the sky, in order to catch them, or commit other such extravagancies. Since ideas are gained by reflection upon sensation, it is further necessary in all cases, in order that an accurate idea of objects may be formed from the sense of sight, that the powers of the mind should be unimpaired, and undisturbed in their exercise. A proof of this is afforded in the instance related by Haslam,[84]of a boy who had no defect of sight, but was weak in understanding, and who in his seventh year was unable to estimate the distances of objects, especially as to height; he would extend his hand frequently towards a nail on the ceiling, or towards the moon, to catch it. It is therefore the judgment which corrects and makes clear this idea, or perception of visible objects."
The intellectual nature of perception as I have shown it, is corroborated physiologically by Flourens[85]as follows:
"Il faut faire une grand distinction entre les sens et l'intelligence. L'ablation d'un tubercule détermine la perte de lasensation, dusensde la vue; la rétine devient insensible, l'iris devient immobile. L'ablation d'un lobe cérébral laisse lasensation, lesens, lasensibilitéde la rétine, lamobilitéde l'iris; elle ne détruit que laperceptionseule. Dans un cas, c'est un faitsensorial; et, dans l'autre, un faitcérébral; dans un cas, c'est la perte dusens; dans l'autre, c'est la perte de laperception. La distinction des perceptions et des sensations est encore un grand résultat; et it est démontré aux yeux. Il y a deux moyens de faire perdre la vision par l'encéphale: 1° par les tubercules, c'est la perte du sens, de la sensation; 2° par les lobes, c'est la perte de la perception, de l'intelligence. La sensibilité n'est donc pas l'intelligence; penser n'est donc pas sentir; et voilà toute une philosophie renversée. L'idée n'est donc pas la sensation; et voilà encore une autre preuve du vice radical de cette philosophie." And again, p. 77, under the heading: Séparation de la Sensibilité et de la Perception:—"Il y a une de mesexpériencesqui sépare nettement lasensibilitéde laperception. Quand on enlève lecerveau proprement dit(lobesouhémisphères cérébraux) à un animal, l'animal perd la vue. Mais, par rapport a l'œil, rien n'est changé: les objets continuent à se peindre sur la rétine; l'irisreste contractile, lenerf optiquesensible, parfaitement sensible. Et cependantl'animal ne voit plus; il n'y a plusvision, quoique tout ce qui estsensationsubsiste; il n'y a plusvision, parce qu'il n'y a plusperception. Lepercevoir, et non lesentir, est donc le premier élément de l'intelligence. Laperceptionest partie de l'intelligence, car elle se perd avec l'intelligence, et par l'ablation du même organe, leslobesouhémisphères cérébraux; et lasensibilitén'en est point partie, puisqu'elle subsiste après la perte de l'intelligenceet l'ablation deslobesouhémisphères."
"Il faut faire une grand distinction entre les sens et l'intelligence. L'ablation d'un tubercule détermine la perte de lasensation, dusensde la vue; la rétine devient insensible, l'iris devient immobile. L'ablation d'un lobe cérébral laisse lasensation, lesens, lasensibilitéde la rétine, lamobilitéde l'iris; elle ne détruit que laperceptionseule. Dans un cas, c'est un faitsensorial; et, dans l'autre, un faitcérébral; dans un cas, c'est la perte dusens; dans l'autre, c'est la perte de laperception. La distinction des perceptions et des sensations est encore un grand résultat; et it est démontré aux yeux. Il y a deux moyens de faire perdre la vision par l'encéphale: 1° par les tubercules, c'est la perte du sens, de la sensation; 2° par les lobes, c'est la perte de la perception, de l'intelligence. La sensibilité n'est donc pas l'intelligence; penser n'est donc pas sentir; et voilà toute une philosophie renversée. L'idée n'est donc pas la sensation; et voilà encore une autre preuve du vice radical de cette philosophie." And again, p. 77, under the heading: Séparation de la Sensibilité et de la Perception:—"Il y a une de mesexpériencesqui sépare nettement lasensibilitéde laperception. Quand on enlève lecerveau proprement dit(lobesouhémisphères cérébraux) à un animal, l'animal perd la vue. Mais, par rapport a l'œil, rien n'est changé: les objets continuent à se peindre sur la rétine; l'irisreste contractile, lenerf optiquesensible, parfaitement sensible. Et cependantl'animal ne voit plus; il n'y a plusvision, quoique tout ce qui estsensationsubsiste; il n'y a plusvision, parce qu'il n'y a plusperception. Lepercevoir, et non lesentir, est donc le premier élément de l'intelligence. Laperceptionest partie de l'intelligence, car elle se perd avec l'intelligence, et par l'ablation du même organe, leslobesouhémisphères cérébraux; et lasensibilitén'en est point partie, puisqu'elle subsiste après la perte de l'intelligenceet l'ablation deslobesouhémisphères."
The following famous verse of the ancient philosopher Epicharmus, proves that the ancients in general recognized the intellectual nature of perception: Νοῦςὁρῇκαὶ νοῦς ἀκούει· τἆλλα κωφὰ καὶ τυφλά. (Mens videt, mens audit; cætera surda et cœca.)[86]Plutarch in quoting this verse, adds:[87]ὡς τοῦ περὶ τὰ ὄμματα καὶ ὦτα πάθους, ἂν μὴ παρῇ τὸ φρονοῦν, αἴσθησιν οὐ ποιοῦντος (quia affectio oculorum et aurium nullum affert sensum, intelligentia absente). Shortly before too he says: Στράτωνος τοῦ φυσικοῦ λόγος ἐστίν, ἀποδεικνύων ὡς οὐδ' αἰσθάνεσθαι τοπαράπαν ἄνευ τοῦ νοεῖν ὑπάρχει. (Stratonis physici exstat ratiocinatio, qua "sine intelligentia sentiri omnino nihil posse" demonstrat.)[88]Again shortly after he says: ὅθεν ἀνάγκη, πᾶσιν, οἷς τὸ αἰσθάνεσθαι, καὶ τὸ νοεῖν ὑπάρχειν, εἰ τῷ νοεῖν αἰσθάνεσθαι πεφύκαμεν (quare necesse est, omnia, quæ sentiunt, etiam intelligere, siquidem intelligendo demum sentiamus).[89]A second verse of Epicharmus might be connected with this, which is quoted by Diogenes Laertes (iii. 16):
Εὔμαιε, τὸ σοφόν ἐστιν οὐ καθ' ἓν μόνον,ἀλλ' ὅσα περ ζῇ, πάντα καὶ γνώμαν ἔχει.
Εὔμαιε, τὸ σοφόν ἐστιν οὐ καθ' ἓν μόνον,ἀλλ' ὅσα περ ζῇ, πάντα καὶ γνώμαν ἔχει.
Εὔμαιε, τὸ σοφόν ἐστιν οὐ καθ' ἓν μόνον,ἀλλ' ὅσα περ ζῇ, πάντα καὶ γνώμαν ἔχει.
Εὔμαιε, τὸ σοφόν ἐστιν οὐ καθ' ἓν μόνον,
ἀλλ' ὅσα περ ζῇ, πάντα καὶ γνώμαν ἔχει.
(Eumaee, sapientia non uni tantum competit, sed quæcunque vivunt etiam intellectum habent.) Porphyry likewise endeavours to show at length that all animals have understanding.[90]
Now, that it should be so, follows necessarily from the intellectual character of perception. All animals, even down to the very lowest, must have Understanding—that is, knowledge of the causal law, although they have it in very different degrees of delicacy and of clearness; at any rate they must have as much of it as is required for perception by their senses; for sensation without Understanding would be not only a useless, but a cruel gift of Nature. No one, who has himself any intelligence, can doubt the existence of it in the higher animals. But at times it even becomes undeniably evident that their knowledge of causality is actuallyà priori, and that it does not arise from the habit of seeing one thing follow upon another. A very young puppy will not, for instance, jump off a table, because he foresees what would be the consequence. Not long ago I had some large curtains put up at my bed-room window, which reached down to the floor, and were drawn aside from the centre by means of a string. The first morning they were opened I was surprised to see my dog, a very intelligent poodle, standing quite perplexed, and looking upwards and sidewards for the cause of the phenomenon: that is, he was seeking for the change which he knewà priorimust have taken place. Next day the same thing happened again.—But even the lowest animals have perception—consequently Understanding—down to the aquatic polypus, which has no distinct organs of sensation, yet wanders from leaf to leaf on its waterplant, while clinging to it with its feelers, in search of more light.
Nor is there, indeed, any difference, beyond that ofdegree, between this lowest Understanding and that of man, which we however distinctly separate from his Reason. The intermediate gradations are occupied by the various series of animals, among which the highest, such as the monkey, the elephant, the dog, astonish us often by their intelligence. But in every case the business of the Understanding is invariably to apprehend directly causal relations: first, as we have seen, those between our own body and other bodies, whence proceeds objective perception; then those between these objectively perceived bodies among themselves, and here, as has been shown in § 20, the causal relation manifests itself in three forms—as cause, as stimulus, and as motive. All movement in the world takes place according to these three forms of the causal relation, and through them alone does the intellect comprehend it. Now, if, of these three,causes, in the narrowest sense of the word, happen to be the object ofinvestigationfor the Understanding, it will produce Astronomy, Mechanics, Physics, Chemistry, and will invent machines for good and for evil; but in all cases a direct, intuitive apprehension of the causal connection will in the last resort lie at the bottom of all its discoveries. For the sole form and function of the Understanding is this apprehension, and not by any means the complicated machinery of Kant's twelve Categories, the nullity of which I have proved.—(All comprehension is a direct, consequently intuitive, apprehension of the causal connection; although this has to be reduced at once to abstract conceptions in order to be fixed. To calculate therefore, is not to understand, and, in itself, calculation conveys no comprehension of things. Calculation deals exclusively with abstract conceptions of magnitudes, whose mutual relations it determines. By it we never attain the slightest comprehension of a physical process, for this requiresintuitivecomprehension of space-relations, by means of which causes take effect.Calculations have merely practical, not theoretical, value. It may even be said thatwhere calculation begins, comprehension ceases; for a brain occupied with numbers is, as long as it calculates, entirely estranged from the causal connection in physical processes, being engrossed in purely abstract, numerical conceptions. The result, however, only shows ushow much, neverwhat. "L'expérience et le calcul," those watchwords of French physicists, are not therefore by any means adequate [for thorough insight].)—If, again,stimuliare the guides of the Understanding, it will produce Physiology of Plants and Animals, Therapeutics, and Toxicology. Finally, if it devotes itself to the study ofmotives, the Understanding will use them, on the one hand, theoretically, to guide it in producing works on Morality, Jurisprudence, History, Politics, and even Dramatic and Epic Poetry; on the other hand, practically, either merely to train animals, or for the higher purpose of making human beings dance to its music, when once it has succeeded in discovering which particular wire has to be pulled in order to move each puppet at its pleasure. Now, with reference to the function which effects this, it is quite immaterial whether the intellect turns gravitation ingeniously to account, and makes it serve its purpose by stepping in just at the right time, or whether it brings the collective or the individual propensities of men into play for its own ends. In its practical application we call the Understandingshrewdnessor, when used to outwit others,cunning; when its aims are very insignificant, it is calledslynessand, if combined with injury to others,craftiness. In its purely theoretical application, we call it simplyUnderstanding, the higher degrees of which are namedacumen,sagacity,discernment,penetration, while its lower degrees are termeddulness,stupidity,silliness, &c. &c. These widely differing degrees of sharpness are innate, and cannot be acquired; although, as I have already shown,even in the earliest stages of the application of the Understanding,i.e.in empirical perception, practice and knowledge of the material to which it is applied, are needed. Every simpleton has Reason—give him the premisses, and he will draw the conclusion; whereasprimary, consequently intuitive, knowledge is supplied by the Understanding: herein lies the difference. The pith of every great discovery, of every plan having universal historical importance, is accordingly the product of a happy moment in which, by a favourable coincidence of outer and inner circumstances, some complicated causal series, some hidden causes of phenomena which had been seen thousands of times before, or some obscure, untrodden paths, suddenly reveal themselves to the intellect.—
By the preceding explanations of the processes in seeing and feeling, I have incontestably shown that empirical perception is essentially the work ofthe Understanding, for which the material only is supplied by the senses in sensation—and a poor material it is, on the whole; so thatthe Understandingis, in fact, the artist, while the senses are but the under-workmen who hand it the materials. But the process consists throughout in referring from given effects to their causes, which by this process are enabled to present themselves as objects in Space. The very fact that we presuppose Causality in this process, proves precisely that this law must have been supplied by the Understanding itself; for it could never have found its way into the intellect from outside. It is indeed the first condition of all empirical perception; but this again is the form in which all external experience presents itself to us; how then can this law of Causality be derived from experience, when it is itself essentially presupposed by experience?—It was just because of the utter impossibility of this, and because Locke's philosophy had put an end to allà priority, that Hume denied the whole reality of the conception ofCausality. He had besides already mentioned two false hypotheses in the seventh section of his "Inquiry concerning the Human Understanding," which recently have again been advanced: the one, that the effect of the will upon the members of our body; the other, that the resistance opposed to our pressure by outward objects, is the origin and prototype of the conception of Causality. Hume refutes both in his own way and according to his own order of ideas. I argue as follows. There is no causal connection whatever between acts of the will and actions of the body; on the contrary, both are immediately one and the same thing, only perceived in a double aspect—that is, on the one hand, in our self-consciousness, or inner sense, as acts of the will; on the other, simultaneously in exterior, spacial brain-perception, as actions of the body.[91]The second hypothesis is false, first because, as I have already shown at length, a mere sensation of touch does not yet give any objective perception whatever, let alone the conception of Causality, which never can arise from the feeling of an impeded muscular effort: besides impediments of this kind often occur without any external cause; secondly, because our pressing against an external object necessarily has a motive, and this already presupposes apprehension of that object, which again presupposes knowledge of Causality.—But the only means of radically proving the conception of Causality to be independent of all experience was by showing, as I have done, that the whole possibility of experience is conditioned by the conception of Causality. In § 23 I intend to show that Kant's proof, propounded with a similar intent, is false.
This is also the proper place for drawing attention to thefact, that Kant either did not clearly recognise in empirical perception the mediation of the causal law—which law is known to us before all experience—or that he intentionally evaded mentioning it, because it did not suit his purpose. In the "Critique of Pure Reason," for instance, the relation between causality and perception is not treated in the "Doctrine of Elements," but in the chapter on the "Paralogisms of Pure Reason," where one would hardly expect to find it; moreover it appears in his "Critique of the Fourth Paralogism of Transcendental Psychology," and only in the first edition.[92]The very fact that this place should have been assigned to it, shows that in considering this relation, he always had the transition from the phenomenon to the thing in itself exclusively in view, but not the genesis of perception itself. Here accordingly he says that the existence of a real external object is not given directly in perception, but can be added to it in thought and thus inferred. In Kant's eyes, however, he who does this is a Transcendental Realist, and consequently on a wrong road. For by his "outward object" Kant here means the thing in itself. The Transcendental Idealist, on the contrary, stops short at the perception of something empirically real—that is, of something existing outside us in Space—without needing the inference of a cause to give it reality. Forperception, according to Kant, is quite directly accomplished without any assistance from the causal nexus, and consequently from the Understanding: he simply identifies perception with sensation. This we find confirmed in the passage which begins, "With reference to the reality of external objects, I need as little trust to inference," &c. &c.[93]and again in the sentence commencing with "Now we may welladmit," &c. &c.[94]It is quite clear from these passages that perception of external things in Space, according to Kant, precedes all application of the causal law, therefore that the causal law does not belong to perception as an element and condition of it: for him, mere sensation is identical with perception. Only in as far as we ask what may, in atranscendentalsense, existoutside of us: that is, when we ask for the thing in itself, is Causality mentioned as connected with perception. Moreover Kant admits the existence, nay, the mere possibility, of causality only in reflection: that is, in abstract, distinct knowledge by means of conceptions; therefore he has no suspicion that its application isanterior to all reflection, which is nevertheless evidently the case, especially in empirical, sensuous perception which, as I have proved irrefragably in the preceding analysis, could never take place otherwise. Kant is therefore obliged to leave the genesis of empirical perception unexplained. With him it is a mere matter of the senses, given as it were in a miraculous way: that is, it coincides with sensation. I should very much like my reflective readers to refer to the passages I have indicated in Kant's work, in order to convince themselves of the far greater accuracy of my view of the whole process and connection. Kant's extremely erroneous view has held its ground till now in philosophical literature, simply because no one ventured to attack it; therefore I have found it necessary to clear the way in order to throw light upon the mechanism of our knowledge.
Kant's fundamental idealistic position loses nothing whatever, nay, it even gains by this rectification of mine, in as far as, with me, the necessity of the causal law is absorbed and extinguished in empirical perception as its product and cannot therefore be invoked in behalf of anentirely transcendent question as to the thing in itself. On referring to my theory above concerning empirical perception, we find that its first datum, sensation, is absolutely subjective, being a process within the organism, because it takes place beneath the skin. Locke has completely and exhaustively proved, that the feelings of our senses, even admitting them to be roused by external causes, cannot have any resemblance whatever to the qualities of those causes. Sugar, for instance, bears no resemblance at all to sweetness, nor a rose to redness. But that they should need an external cause at all, is based upon a law whose origin lies demonstrably within us, in our brain; therefore this necessity is not less subjective than the sensations themselves. Nay, evenTime—that primary condition of every possiblechange, therefore also of the change which first permits the application of the causal law—and not lessSpace—which alone renders the externalisation of causes possible, after which they present themselves to us as objects—even Time and Space, we say, are subjective forms of the intellect, as Kant has conclusively proved. Accordingly we find all the elements of empirical perception lying within us, and nothing contained in them which can give us reliable indications as to anything differing absolutely from ourselves, anything in itself.—But this is not all. What we think under the conceptionmatter, is the residue which remains over after bodies have been divested of their shape and of all their specific qualities: a residue, which precisely on that account must be identical in all bodies. Now these shapes and qualities which have been abstracted by us, are nothing but the peculiar, specially definedway in which these bodies act, which constitutes precisely their difference. If therefore we leave these shapes and qualities out of consideration, there remains nothing butmere activity in general, pure action as such, Causality itself, objectively thought—thatis, the reflection of our own Understanding, the externalised image of its sole function; and Matter is throughout pure Causality, its essence is Action in general.[95]This is why pure Matter cannot be perceived, but can only be thought: it is a something we add to every reality, as its basis, in thinking it. For pure Causality, mere action, without any defined mode of action, cannot become perceptible, therefore it cannot come within any experience.—Thus Matter is only the objective correlate to pure Understanding; for it is Causality in general, and nothing else: just as the Understanding itself is direct knowledge of cause and effect, and nothing else. Now this again is precisely why the law of causality is not applicable to Matter itself: that is to say, Matter has neither beginning nor end, but is and remains permanent. For as, on the one hand, Causality is the indispensable condition of all alternation in the accidents (forms and qualities) of Matter,i.e.of all passage in and out of being; but as, on the other hand, Matter is pure Causality itself, as such, objectively viewed: it is unable to exercise its own power upon itself, just as the eye can see everything but itself. "Substance" and Matter being moreover identical, we may callSubstance,actionviewedin abstracto:Accidents, particular modes of action, actionin concreto.—Now these are the results to which true,i.e.transcendental, Idealism leads. In my chief work I have shown that the thing in itself—i.e.whatever, on the whole, exists independently of our representation—cannot be got at by way of representation, but that, to reach it, we must follow quite a different path, leading through the inside of things, which lets us into the citadel, as it were, by treachery.—
But it would be downright chicanery, nothing else, totry and compare, let alone identify, such an honest, deep, thorough analysis of empirical perception as the one I have just given, which proves all the elements of perception to be subjective, with Fichte's algebraic equations of theEgoand theNon-Ego; with his sophistical pseudo-demonstrations, which in order to be able to deceive his readers had to be clothed in the obscure, not to say absurd, language adopted by him; with his explanations of the way in which theEgospins theNon-Egoout of itself; in short, with all the buffoonery of scientific emptiness.[96]Besides, I protest altogether against any community with this Fichte, as Kant publicly and emphatically did in a noticead hocin the "Jenaer Litteratur Zeitung."[97]Hegelians and similar ignoramuses may continue to hold forth to their heart's content upon Kant-Fichteian philosophy: there exists a Kantian philosophy and a Fichteian hocus-pocus,—this is the true state of the case, and will remain so, in spite of those who delight in extolling what is bad and in decrying what is good, and of these Germany possesses a larger number than any other country.
Thus it is from the sensations of our body that we receive the data for the very first application of the causal law, and it is precisely by that application that the perception of this class of objects arises. They therefore have their essence and existence solely in virtue of the intellectual function thus coming into play, and of its exercise.
Now, as far as it is the starting-point,i.e.the mediator, for our perception of all other objects, I have called the bodily organism, in the first edition of the present work, theImmediate Object; this, however, must not be taken in a strictly literal sense. For although our bodily sensations are all apprehended directly, still this immediate apprehension does not yet make our body itself perceptible to us as an object; on the contrary, up to this point all remains subjective, that is to say, sensation. From this sensation certainly proceeds the perception of all other objects as the causes of such sensations, and these causes then present themselves to us as objects; but it is not so with the body itself, which only supplies sensations to consciousness. It is onlyindirectlythat we know even this body objectively,i.e.as an object, by its presenting itself, like all other objects, as the recognised cause of a subjectively given effect—and precisely on this accountobjectively—in our Understanding, or brain (which is the same). Now this can only take place when its own senses are acted upon by its parts: for instance, when the body is seen by the eye, or felt by the hand, &c., upon which data the brain (or understanding) forthwith constructs it as to shape and quality in space.—The immediate presence in our consciousness of representations belonging to this class, depends therefore upon the position assigned to them in the causal chain—by which all things areconnected—relatively to the body (for the time being) of the Subject—by which (the Subject) all things areknown.
One of the chief objects of the "Critique of Pure Reason" is to show the universal validity, for all experience, of the causal law, itsà priority, and, as a necessaryconsequence of this, its restriction to possible experience. Nevertheless, I cannot assent to the proof there given of theà priorityof the principle, which is substantially this:—"Thesynthesisof the manifold by the imagination, which is necessary for all empirical knowledge, gives succession, but not yet determinate succession: that is, it leaves undetermined which of two states perceived was the first, not only in my imagination, but in the object itself. But definite order in this succession—through which alone what we perceive becomes experience, or, in other words, authorizes us to form objectively valid judgments—is first brought into it by the purely intellectual conception of cause and effect. Thus the principle of causal relation is the condition which renders experience possible, and, as such, it is given usà priori."[98]
According to this, the order in which changes succeed each other in real objects becomes known to us as objective only by their causality. This assertion Kant repeats and explains in the "Critique of Pure Reason," especially in his "Second Analogy of Experience,"[99]and again at the conclusion of his "Third Analogy," and I request every one who desires to understand what I am now about to say, to read these passages. In them he affirms everywhere thatthe objectivity of the succession of representations—which he defines as their correspondence with the succession of real objects—is only known through the rule by which they follow upon one another: that is, through the law of causality; that my mere apprehension consequently leaves the objective relation between phenomena following one another quite undetermined: sinceI merely apprehend the succession of my own representations, but the succession in my apprehension does not authorize me to form any judgment whatever as to the succession in the object, unless that judgment be based upon causality; and since, besides, I might invert the order in which these perceptions follow each other in my apprehension, there being nothing which determines them as objective. To illustrate this assertion, Kant brings forward the instance of a house, whose parts we may consider in any order we like, from top to bottom, or from bottom to top; the determination of succession being in this case purely subjective and not founded upon an object, because it depends upon our pleasure. In opposition to this instance, he brings forward the perception of a ship sailing down a river, which we see successively lower and lower down the stream, which perception of the successively varying positions of the ship cannot be changed by the looker-on. In this latter case, therefore, he derives the subjective following in his own apprehension from the objective following in the phenomenon, and on this account he calls it anevent. Now I maintain, on the contrary, thatthere is no difference at all between these two cases, that both are events, and that our knowledge of both is objective: that is to say, it is knowledge of changes in real objects recognized as such by the Subject.Both are changes of relative position in two bodies.In the first case, one of these bodies is a part of the observer's own organism, the eye, and the other is the house, with respect to the different parts of which the eye successively alters its position. In the second, it is the ship which alters its position towards the stream; therefore the change occurs between two bodies. Both are events, the only difference being that, in the first, the change has its starting-point in the observer's own body, from whose sensations undoubtedly all his perceptions originally proceed, but which is nevertheless an objectamong objects, and in consequence obeys the laws of the objective, material world. For the observer, as a purely cognising individual, any movement of his body is simply an empirically perceived fact. It would be just as possible in the second as in the first instance, to invert the order of succession in the change, were it as easy for the observer to move the ship up the stream as to alter the direction of his own eyes. For Kant infers the successive perception of different parts of the house to be neither objective nor an event, because it depends upon his own will. But the movement of his eyes in the direction from roof to basement is one event, and in the direction from basement to roof another event, just as much as the sailing of the ship. There is no difference whatever here, nor is there any difference either, as to their being or not being events, between my passing a troop of soldiers and their passing me. If we fix our eyes on a ship sailing close by the shore on which we are standing, it soon seems as if it were the ship that stood still and the shore that moved. Now, in this instance we are mistaken, it is true, as to the cause of the relative change of position, since we attribute it to a wrong cause; the real succession in the relative positions of our body towards the ship is nevertheless quite rightly and objectively recognised by us. Even Kant himself would not have believed that there was any difference, had he borne in mind that his own body was an object among objects, and that the succession in his empirical perceptions depended upon the succession of the impressions received from other objects by his body, and was therefore an objective succession: that is to say, one which takes place among objectsdirectly(if not indirectly) and independently of the will of the Subject, and which may therefore be quite well recognised without any causal connection between the objects acting successively on his body.
Kant says, Time cannot be perceived; therefore no succession of representations can be empirically perceived as objective:i.e.can be distinguished as changes in phenomena from the changes of mere subjective representations. The causal law, being a rule according to which states follow one another, is the only means by which the objectivity of a change can be known. Now, the result of his assertion would be, that no succession in Time could be perceived by us as objective, excepting that of cause and effect, and that every other succession of phenomena we perceive, would only be determined so, and not otherwise, by our own will. In contradiction to all this I must adduce the fact, that it is quite possible for phenomena tofollow uponone another withoutfollowing fromone another. Nor is the law of causality by any means prejudiced by this; for it remains certain that each change is the effect of another change, this being firmly establishedà priori; only each change not only follows upon the single one which is its cause, but upon all the other changes which occur simultaneously with that cause, and with which that cause stands in no causal connection whatever. It is not perceived by me exactly in the regular order of causal succession, but in quite a different order, which is, however, no less objective on that account, and which differs widely from any subjective succession depending on my caprice, such as, for instance, the pictures of my imagination. The succession, in Time, of events which stand in no causal connection with each other is precisely what we callcontingency.[100]Just as I am leaving my house, a tile happens to fall from the roof which strikes me; now, there is no causal connection whatever between my going out andthe falling of the tile; yet the order of their succession—that is, that my going out preceded the falling of the tile—is objectively determined in my apprehension, not subjectively by my will, by which that order would otherwise have most likely been inverted. The order in which tones follow each other in a musical composition is likewise objectively determined, not subjectively by me, the listener; yet who would think of asserting that musical tones follow one another according to the law of cause and effect? Even the succession of day and night is undoubtedly known to us as an objective one, but we as certainly do not look upon them as causes and effects of one another; and as to their common cause, the whole world was in error till Copernicus came; yet the correct knowledge of their succession was not in the least disturbed by that error. Hume's hypothesis, by the way, also finds its refutation through this; since the following of day and night upon each other—the most ancient of all successions and the one least liable to exception—has never yet misled anyone into taking them for cause and effect of each other.