ANALYSIS OF THE OBJECTIVENESS OF SENSATIONS.
37. Is the external world such as we believe it to be? Are the beings, calledbodies, which cause our sensations in reality what we believe them? May we not, even after having demonstrated the existence of these beings, and their necessary subjection to constant laws, still doubt whether we have demonstrated the existence of bodies? Does it suffice for this to have proved the existence of external beings in relation among themselves and with us by means of laws fixed and independent of them as of ourselves?
38. Thoroughly to understand this question, it will be well to simplify it, and confine it to a single object.
I hold in my hand and see an orange. I am certain, from what has just been demonstrated, that an external object exists in relation with other beings, and with myself, by necessary laws; I am also certain that I may receive different impressions from it; I see its color, size, and shape, perceive its odor, try its taste; feel in my hand its size, weight, and form, its concavities and convexities, and also hear a little noise when I press it with my hand.
The idea of body is composite, and such is that of the orange; for it is that of something external, extended, colored, odorous, and savory. Whenever all these circumstances exist together, whenever I receive from an object these same impressions, I say that I see an orange.
39. Let us now examine how far the object corresponds to the sensations it causes in us.
What do we mean when we say a thing is savory? Simply, that it produces an agreeable impression upon our palate; and the same is true of smell. Therefore, the two words, odorous and savory, express only thecausalityof these sensations resident in the external object. We may say the same of color, for, although we commonly transfer the sensation to the object, and openly contradict the philosophical theory of light and color, this contradiction is less real than apparent; for the judgment well examined is found to consist only in referring the impression to determinate objects; so that when we for the first time hear professors of physics tell us that colors are not in the object, we easily accustom ourselves to reconcile the philosophical theory with the impression of the sense; especially since this theory does not render it less true that this or that impression comes to us from this or that object, or its different parts.
40. Here, it is not difficult to explain the phenomena of sensation or their correspondence with external objects; for the correspondence is saved if these objects be really the cause (or occasion) of the sensations. The question of extension is more difficult; for this is as the basis of all other sensible properties; and abstracting its constituting or not constituting the essence of bodies, it is certain that we know no body without extension.
41. The following observation will render palpable the difference between extension and other sensible qualities. He who has never thought of the relation of external objects to his sensations is indescribably confused; he in some sense transfers color, odor, taste, and even sound, to objects themselves, and considers confusedly these things to be qualities inherent in them. Thus the child and the uneducated man believe the color green to be really in the foliage, odor in the rose, sound in the bell, taste in the fruit. Butthis is readily seen to be a confused judgment, of which they render no perfectly clear account to themselves; a judgment which may be changed or even destroyed without changing or destroying the relations of our sensations with their objects. Even at a very tender age we easily accustom ourselves to refer color to light, and even not to fix it definitively, but to regard it as an impression produced upon our sense by the action of that mysterious agent. It costs us no more to consider smell as a sensation produced by the action of the effluvia of bodies upon the organ of smell; we also cease to consider sound as something inherent in the sonorous body, and come to see in it only the impression caused upon the sense by the vibration of the air, excited in its turn by the vibration of the sonorous body.
These philosophical considerations may, at first sight, seem to be in contradiction to our judgment, but they do not change to us the external world; they cause no inversion of our ideas of it; they only make us fix our attention upon some relations which we had imperfectly defined, and do not allow us to attribute to objects what in reality does not belong to them. They make us limit the testimony of the senses to their appropriate sphere, and in some manner rectify our judgments; but the world continues the same that it was before, excepting that we have discovered in the marvels of nature a closer relation with our own being, and have perceived that our organization and our soul play a more important part in them than we had imagined.
42. If we destroy extension, take this quality from external objects, and regard it as only a mere sensation, of which we only know that there is an external object which causes it, the corporeal world at once disappears. The whole system of the universe will be reduced to a collection of beings which cause us different impressions; without the idea of extension we can neither form any idea of body, norknow if all that we have thought of the world be aught else than a pure illusion. I can easily resign my infantile belief that the color I see in my hand is in it, or the noise made when I clap my hands is in them; but I cannot, do what I will, lay aside the idea of extension; I cannot imagine the distance from my wrist to the extremity of my fingers to be only a pure illusion, that there only exists a being which causes it without my knowing whether in reality this distance exists. I can easily separate from the fruit which I find savory the quality of savor; and I may, if I examine it philosophically, admit, without any inconvenience, that it has nothing resembling taste, but that it is only composed so to affect my palate as to produce an agreeable sensation. But I cannot take from the fruit its extension; in no wise can I regard it as something indivisible; I cannot possibly regard the distance from one of its points to another as a mere sensation. My efforts to consider the savory object as in itself indivisible are all in vain; and if, for a single instant, I seem to have overcome the instinct of nature, every thing is overturned. By the same right that I make the fruit something indivisible, I may make the whole universe so; but an indivisible universe is to me no universe; my intellect is confounded, and all around me is annihilated. I am in worse than chaos; for chaos is at least something, although the elements are in horrible confusion and frightful darkness; but now I am worse off, for the corporeal world, such as I have conceived it to be, returns to nothing.