*The Common Sensibles and the Common Sense-organ*.--Every sense has a range of qualities connected with it as its special objects. Colours can only be perceived by the eye, sounds by the ear, and so forth. But there are certain characters of perceived things which we appear to apprehend by more than one sense. Thus we seem to perceive size and shape either by touch or by sight, and number by hearing as well, since we can count _e.g._ the strokes of an unseen bell. Hence Aristotle distinguishes between the "special sensible qualities" such as colour and pitch, and what he calls the "common sensibles," the character of things which can be perceived by more than one organ. These are enumerated as size, form or shape, number, motion (and its opposite rest), being. (The addition of this last is, of course, meant to account for our conviction that any perceived colour, taste, or other quality is a reality and not a delusion.) The list corresponds very closely with one given by Plato of the "things which the mind perceives _by herself without the help of any organ_," _i.e._ of the leading determinations of sensible things which are due not to sense but to understanding. It was an unfortunate innovation to regard the discernment of number or movement, which obviously demand intellectual processes such as counting and comparison, as performed immediately by "sense," and to assign the apprehension of number, movement, figure to a central "organ." This organ he finds in the heart. The theory is that when the "special organs" of the senses are stimulated, they in turn communicate movements to the blood and "animal spirits" (_i.e._ the vapours supposed to be produced from the blood by animal heat). These movements are propagated inwards to the heart, where they all meet. This is supposed to account for the important fact that, though our sensations are so many and diverse, we are conscious of our own unity as the subjects apprehending all this variety. The unity of the perceiving subject is thus made to depend on the unity of the ultimate "organ of sensation," the heart. Further, when once a type of motion has been set up in any sense-organ at the periphery of the body it will be propagated inward to the "common sensorium" in the heart. The motions set up by stimulation, _e.g._ of the eye and of the skin, are partly different, partly the same (viz. in so far as they are determined by the number, shape, size, movement of the external stimuli). Hence in the heart itself the stimulation on which perception of number or size depends is one and the same whether it has been transmitted from the eye or from the skin! Awareness of lapse of time is also regarded as a function of the "common sense-organ," since it is the "common sensory" which perceives motion, and lapse of time is apprehended only in the apprehension of motion. Thus, in respect of the inclusion of geometrical form and lapse of time