Accordingly, when it is said that Plato was "deeply struck {280} with the importance of Classification," we must understand the phrase as applying to Classification, not as he found it prevalent, but as he idealized it. And the scheme that he imagined was not merely different from that which he found, but in direct repugnance to it. He denounced altogether the aggregate of individuals; he declared the class-constituent to reside in a reality apart from them, separate and self-existent--the Idea or Form. He enjoined the student of philosophy to fix his contemplation on these Class-Ideas, the real Realities, in their own luminous region: and for that purpose, to turn his back upon the phenomenal particulars, which were mere transitory, shadowy, incoherent projections of these Ideas[j]--and from the study of which no true knowledge could be obtained. Of the two statements in the Analysis--(p. 271) that "Plato never dreamed of the mystical visions of his successors," and that "his error (respecting Classification) lay in misconceiving the One; which he took, not for the aggregate, but something pervading the aggregate"--neither one nor the other appears to me accurate. In regard to the second of the two, indeed, you may find various passages of Plato which, if construed separately, would countenance it: for Plato does not always talk Realism--nor always consistently with himself. But still his capital and peculiar theory was, Realism. The Platonic One was not something pervading the aggregate of particulars, but an independent and immutable reality, apart from the aggregate: and Plato, when he thus conceived {281} the One, illustrating it by the vast hypotheses embodied in the Republic, Phædon, Phædrus, Symposion, Menon, &c., is the true originator of those "mystical visions" against which the Analysis justly protests. Such visions were doubtless suggested to Plato by "his deep sense of the importance of Classification:" but they are his own, though continued and amplified, without his decorative genius, by Neo-Platonic successors. His theory of classification was the first ever propounded; and that theory was Realism. The doctrine here ascribed to him by Mr. James Mill is much more Aristotelian than Platonic. The main issue raised by Aristotle against Plato was, upon the essential separation, and separate objective existence, of the Abstract and Universal: Plato affirmed it, Aristotle denied it.[k] Aristotle recognised no reality apart from the Particular, to which the Universal was attached as a predicate, either essential or accidental to its subject. The Aristotelian Universal may thus be called, in relation to a body of similar particulars, not the aggregate but something pervading the aggregate. But this is not Plato's view: it is the negation of the Platonic Realism.