III.—CLASSIFICATION OF THE PLATONIC SYSTEM.—The philosophy of Plato, as left by himself, is without a systematic statement, and has no comprehensive principle of classification. He has given us only the history of his thinking, the statement of his philosophical development; we are therefore limited in reference to his classification of philosophy to simple intimations. Accordingly, some have divided the Platonic system into theoretical and practical science, and others into a philosophy of the good, the beautiful and the true. Another classification, which has some support in old records, is more correct. Some of the ancients say that Plato was the first to unite in one whole the scattered philosophical elements of the earlier sages, and so to obtain for philosophy the three parts, logic, physics, and ethics. The more accurate statement is given by _Sextus Empiricus_, that Plato has laid the foundation for this threefold division of philosophy, but that it was first expressly recognized and affirmed by his scholars, Xenocrates and Aristotle. The Platonic system may, however, without difficulty, be divided into these three parts. True, there are many dialogues which mingle together in different proportions the logical, the ethical, and the physical element, and though even where Plato treats of some special discipline, the three are suffered constantly to interpenetrate each other, still there are some dialogues in which this fundamental scheme can be clearly recognized. It cannot be mistaken that the Timæus has predominantly a physical, and the Republic as decidedly an ethical element, and if the dialectic is expressly represented in no separate dialogue, yet does the whole Megaric group pursue the common end of bringing out the conception of science and its true object, being, and is, therefore, in its content decidedly dialectical. Plato must have been led to this threefold division by even the earlier development of philosophy, and though Xenocrates does not clearly see it, yet since Aristotle presupposes it as universally admitted, we need not scruple to make it the basis on which to represent the Platonic system. The order which these different parts should take, Plato himself has not declared. Manifestly, however, dialectics should have the first place as the ground of all philosophy, since Plato uniformly directs that every philosophical investigation should begin with accurately determining the _idea_ (_Phæd._ p. 99. Phædr. p. 237), while he subsequently examines all the concrete spheres of science on the standpoint of the doctrine of ideas. The relative position of the other two parts is not so clear. Since, however, the physics culminates in the ethics, and the ethics, on the other hand, has for its basis physical investigations into the ensouling power in nature, we may assign to physics the former place of the two.