5. In what does sensation consist? What is its internal nature? We only know that it is a modification of our being, and that we cannot explain it. No words suffice to convey an idea of a sensation to one who has never experienced it. The man born blind may listen to all that philosophers have said and written on light and colors, but can never imagine what light and colors are.
Experience is the only teacher here; and thus, if we suppose a man's senses to be changed so that green appears to him purple, and purple green, notwithstanding his constant communication with other men, he will never be freed from his error, and he will never suspect that during his whole life he has made use of the words green and purple in a different sense from other men.
6. Analogy and nature incline us to believe that brutes are not mere machines, but that they also have sensations. The vast scale over which irrational beings are distributed, shows that the faculty of feeling is spread over the universe in different degrees, and with a wonderful profusion.
Our experience is confined to the globe in which we live; but are the limits of sensitive life the same as those of our experience? Even on this globe our observation is confined to what the imperfection of our senses, and the instruments which we use, permit; but how far is the chain of life prolonged? Where is its term? Is there not some participation of this mysterious faculty in those beings which we hold to be inanimate? Is the universe, as Leibnitz pretends, composed of a collection of monads endowed with a certain perception? This is indeed an unfounded hypothesis; but since our means of observation are so limited, we should be cautious how we assign boundaries to the realm of life.
7. We ordinarily speak of the faculty of sensation as of something belonging to a very inferior order; so it is, in fact, if compared with intellectual faculties; but this does not prevent it, in itself considered, from being a wonderful phenomenon, of a nature to astonish and confound all who meditate upon it.
Sensation! With this word alone we pass an immense gap in the scale of beings. What is the non-sensible compared with the sensible? The insensible is, but experiences not that it is; there is nothing in it but itself: the sensible experiences that it is; and there is in it something besides itself, all that it feels, all that is represented in it. The insensible, although surrounded with beings, is in complete isolation,—in solitude; the sensible, although alone, may be in a world of infinitely varied representations.
8. The idea of the me is in some sense applicable to every sensitive being; for sensation is inconceivable without a permanent being, which experiences what is transitory; that is, without a being which is one in the midst of multiplicity. Every sensible being, were it capable of reflection, might, in its own way, say I; for it is true of all of them that it is one same being that experiences the variety of sensations. Without this bond, this unity, there is no one sensible being, but a succession of sensations as unconnected phenomena of the whole.
9. There is no sensation without direct consciousness; for, as this is nothing but the very presence of the phenomenon to the being experiencing it, it would be contradictory to say that it feels without consciousness. A sensation experienced, is a sensation present; a sensation not present, that is, not experienced, is inconceivable, is an absurdity.[35]
10. Every sensation involves presence, or direct consciousness, but not representation. I think this distinction important. The sensations of smell, taste, and hearing, are not representative; they remain in themselves, and in their object. The being experiencing them might believe himself enclosed in himself, in an absolute solitude, with no relation to other beings; but touch, and, above all, sight, are by their nature representative; they involve relation to objects; and they imply relation to other beings, not as to mere causes of the internal affection, but as the originals represented in the sensation.
The class of sensible beings endowed with the faculty of representation seems to be of an order very superior to the others; these beings not only have consciousness, but also a mysterious power whereby they see within themselves an entire world.