De Anima

In regard to all sense generally we must understand that sense is that which is receptive of sensible forms apart from their matter, as wax receives the imprint of the signettion: seal ring apart from the iron or gold of which it is made: it"pon we*- takes the imprint which is of gold or bronze, but not gold or bronze. And similarly sense as relative to each sensible is acted upon by that which possesses colour, flavour or sound, not in so far as each of those sensibles is called a particular thing, but in so far as it possesses a particular quality and in respect of its character or form. The primary sense-organ is that in and organ. which such a power resides, the power to receive sensible forms. Thus the organ is one and the same with the power, but logically distinct from it. For that which perceives must be an extended magnitude. Sensitivity, however, is not an extended magnitude, nor is the sense: they are rather a certain character or power of the organ. From this it is evident why excesses in the sensible objects destroy the sense-organs. For if the motion is too violent for the sense-organ, the character or form (and this, as we Saw, constitutes the sense) is annulled, just as the harmony and the pitch of the lyre suffer by too violent jangling of the strings. It is evident, again, why plants have no sensation, although they have one part of soul and are in some degree affected by the things themselves which are tangible: for example, they become cold and hot. The reason is that they have in them no mean, no principle capable of receiving the forms of sensible objects without their matter, but on the contrary, when they are acted upon, the matter acts upon them as well. It might be asked whether what is unable to smell would be in any way acted upon by an odour, or that which is incapable of seeing by a colour, and so for the other sensibles. But, if the object of smell is odour, the effect it produces, if it produces an effect at all, is smelling. Therefore none of the things that are unable to smell can be acted upon by odour, and the same is true of the other senses: nor can things be acted upon when they have the power of sensation, except as they individually possess the particular sense required. This may also be shown as follows. Light and darkness do not act upon bodies at all; neither does sound nor odour: it is the things which possess them that act. Thus it is the air accompanying the thunderbolt which rives the timber. But, it may be said, things tangible and

flavours do so act: else by what agency are inanimate things acted upon or changed? Shall we, then, conclude that the objects of the other senses likewise act directly? Is it not rather the case that not all body can be affected by smell and sound, and that the bodies which are so affected are indeterminate and shifting; for example, air? For odour in the air implies that the air has been acted upon in some way. What then is smelling, besides a sort of suffering or being acted upon? Or shall we say that the act of smelling implies sense-perception, whereas the air, after it has been acted upon, so far from perceiving, at once becomes itself perceptible to sense?