and yet one which may not be altogether devoid of truth, and which, at any rate, may furnish food for meditation.
4. But my principal reason for alluding to this dogma is on account of the prominent place which has been assigned to it by Sir W. Hamilton in the history of philosophy. From this maxim, "Similia similibus cognoscuntur," he derives the theory of a representative perception; that theory which it was the business of Dr Reid's life to overturn. The theory was, that the mind had no immediate cognisance of external objects, no cognisance of objects themselves, but only of certain vicarious images or representations of them. On what ground does this opinion rest? It rests, says Sir William, on the dogma that like can be known only by like. Real things being unlike the mind—the mind being spiritual, while they are material—they cannot be known by the mind; they cannot be its direct or immediate objects, but their images, being incorporeal—in other words, being of a nature analogous or like to the mind—can be known, and are alone known, by the mind in the intercourse which it holds with external things. Deny this dogma, then, affirm its opposite, that the mind can know what is altogether unlike itself, and of a different nature from itself, and you cut away the ground on which the doctrine of a representative perception rests. Such is the purport of Sir W. Hamilton's statement. You will find the
