IS THE EXTERNAL AND IMMEDIATE CAUSE OF SENSATIONS A FREE CAUSE?
32. A difficulty, at first sight serious, but in reality futile, may be brought against the existence of bodies. Who knows, it may be asked, but what some cause, not at all resembling the idea which we form of bodies, produces in us all the phenomena that we experience? God may, if he pleases, cause one or many sensations in us; and who shall assure us that he does not? Who shall assure us that other beings may not do the same, and so all our imaginations of a corporeal world be a pure illusion?
33. The first and simplest solution that can be given is, that God, being infinitely true, can neither deceive us himself, nor allow other creatures to deceive us constantly and in a way that we cannot resist. But this solution although well founded, just, and reasonable, labors under the inconvenience of establishing the physical by recurring to the moral order; and so it would never satisfy those who desire to see the truth of the testimony of the senses demonstrated by arguments drawn from the nature of things. Such arguments we think we can supply.
34. Our sensations do not proceedimmediatelyfrom a free cause; the being that produces them, as well as thatwhich experiences them, is subject to fixed and necessary laws. To be convinced of this, we have only to reflect that we cannot, if placed in certain conditions, fail to experience a determinate sensation, and that if these conditions be wanting, we cannot experience it. And this proves that we, as well as the being which causes the impression in us, are subject to a necessary order. Were it not thus, we could not produce the sensation even by the means of certain conditions; for as its cause would be subject to no law, but only to its own free will, it might a thousand times happen, that our will would not agree with its will, and so the desired impression would not be produced.
After experiencing a sensation of touch in which it seems that an opaque body covers our eyes, we do not see, and we cannot with all our efforts produce, the sensation calledseeing; on the other hand, if at a corresponding hour and place this sensation of contact ceases to exist, we cannot possibly fail to experience the sensation of seeing different objects. Here, therefore, we are subject to a necessity; the being, also, that causes the sensations in us, is subject to a like necessity; for if we perform the condition once or a thousand times of closing our eyes, once or a thousand times the sensation will disappear; or if we open them once or a thousand times in a light place, so many times also the sensation will be produced; the same, if we retain everything in the same state, and varied at our pleasure, if we change our situation or the objects around us. There does, therefore, exist without us, subject to necessary laws, a collection of beings which produce our sensations.
35. It is remarkable not only that the influence they exert upon us does not flow from election or spontaneity in them, but that they are not even presented as endowed with an activity of their own. A painting hung upon the wall produces in us the same sensation as often as we lookat it; and, saving the deterioration of time, it will continue for ever to produce the same sensation.
It is, moreover, evident that these beings are subject to our action, for we can, by acting upon them differently, make them produce different impressions. We touch a ball, and the continuation of the sensation of a hard, polished, spherical body, assures us that it is one and the same being that produces it for a certain length of time; and yet, in this interval, we may receive many and various sensations from the same object, by presenting it to the light in different ways.
36. The subjection of these beings to necessary laws is not necessarily with respect to sensations, but is rather a mutual connection of their own. The connection of impressions which we receive from them is an effect of the dependence of some of them upon others; so that, in order to produce a determinate impression, we often employ an object which is, in itself considered, of no direct use, but which brings another into action, and so leads to what we desire. To raise a curtain has no connection with a magnificent landscape; and yet, oftentimes, we do nothing else when we wish to obtain a pleasant prospect. The relation in question is not then of sensations, but of their objects; the connection of these is what induces us to make use of one of them in order to obtain another. There is, therefore, outside of us a collection of beings subject to fixed laws, as well with respect to our sensations as to themselves mutually; therefore the external world exists, and the internal world, which represents it to us, is not a pure illusion.