2. When, then, we see any corporeal object, these three things, as is most easy to do, are to be considered and distinguished: First, the object itself which we see; whether a stone, or flame, or any other thing that can be seen by the eyes; and this certainly might exist also already before it was seen; next, vision or the act of seeing, which did not exist before we perceived the object itself which is presented to the sense; in the third place, that which keeps the sense of the eye in the object seen, so long as it is seen, viz. the attention of the mind. In these three, then, not only is there an evident distinction, but also a diverse nature. For, first, that visible body is of a far different nature from the sense of the eyes, through the incidence of which sense upon it vision arises. And what plainly is vision itself other than perception informed by that thing which is perceived? Although there is no vision if the visible object be withdrawn, nor could there be any vision of the kind at all if there were no body that could be seen; yet the body by which the sense of the eyes is informed, when that body is seen, and the form itself which is imprinted by it upon the sense, which is called vision, are by no means of the same substance. For the body that is seen is, in its own nature, separable; but the sense, which was already in the living subject, even before it saw what it was able to see, when it fell in with something visible,—or the vision which comes to be in the sense from the visible body when now brought into connection with it and seen,—the sense, then, I say, or the vision, that is, the sense informed from without, belongs to the nature of the living subject, which is altogether other than that body which we perceive by seeing, and by which the sense is not so formed as to be sense, but as to be vision. For unless the sense were also in us before the presentation to us of the sensible object, we should not differ from the blind, at times when we are seeing nothing, whether in darkness, or when our eyes are closed. But we differ from them in this, that there is in us, even when we are not seeing, that whereby we are able to see, which is called the sense; whereas this is not in them, nor are they called blind for any other reason than because they have it not. Further also, that attention of the mind which keeps the sense in that thing which we see, and connects both, not only differs from that visible thing in its nature; in that the one is mind, and the other body; but also from the sense and the vision itself: since this attention is the act of the mind alone; but the sense of the eyes is called a bodily sense, for no other reason than because the eyes themselves also are members of the body; and although an inanimate body does not perceive, yet the soul commingled with the body perceives through a corporeal instrument, and that instrument is called sense. And this sense, too, is cut off and extinguished by suffering on the part of the body, when any one is blinded; while the mind remains the same; and its attention, since the eyes are lost, has not, indeed, the sense of the body which it may join, by seeing, to the body without it, and so fix its look thereupon and see it, yet by the very effort shows that, although the bodily sense be taken away, itself can neither perish nor be diminished. For there remains unimpaired a desire [appetitus] of seeing, whether it can be carried into effect or not. These three, then, the body that is seen, and vision itself, and the attention of mind which joins both together, are manifestly distinguishable, not only on account of the properties of each, but also on account of the difference of their natures.