Let us, before proceeding further, speak upon the objects of perception in relation to each of the senses. The object of perception is spoken of in a three-fold manner, as there are two ways in which we speak of perceiving objects distinctly, and one in which we speak of perceiving them accidentally; and of those two ways one signifies the property which is peculiar to each sense, and the other the property which is common to all the senses. I mean by peculiar property that which cannot be perceived by any other than its own sense, and concerning which that sense cannot be deceived—as colour for sight, sound for hearing, and savour for taste. The touch, indeed, discriminates several differences of quality, but every other sense distinguishes only its own subjects; and thus sight or hearing is never deceived as to whether it is colour or sound which is seen or heard, although it may be deceived as to what or where the coloured, what or where the sonorous body may be.
Such then the properties which are said to be peculiar and to belong to particular senses; but there
