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CH. III.] suffice for thinking, that there should be contact by some one of its parts, why should it move in a circle, or why be magnitude? And if necessary for thinking that there should be contact by the whole circle, then what means contact by its parts? How, besides, shall that which has parts think by that which is without parts, or that which is without by that which has parts ? Thus, it follows that the mind must be that circle: for thinking is the movement of the mind, as the periphery is the movement of the circle ; and, if thinking be the periphery of the mind, the mind may be regarded as the circle, of which thinking is the periphery. But then the mind will be ever thinking, and necessarily so, since the peripheral movement is unceasing. Now, there are limits to practical thoughts, (as all such are for the sake of something else,) and so equally there are to speculative thoughts, in their reasons; and every reason is either a definition or a demonstration. Thus, demonstrations set out from a principle, and are, in some way, terminated by a syllogism or a conclusion; and even though not concluded, they do not revert to their principle, but, taking up another mean and extreme, they proceed onward; but the periphery, on the contrary, does revert to its point of departure. Definitions, however, are always limited. If, moreover, the same periphery recur often, the mind will be driven to think often upon the same subject, and