The starting-point of the Platonic philosophy, as, indeed, it must he of all philosophy, properly so called, is the theory of knowledge. This is set forth in the Thetetelus, the Sophistes, and the Parmenides; and in the Cratylus, the foundations are laid for ascience of language, as the necessary product of a creature energizing by ideas. The Platonic theory of knowledge., as developed in the Theadetus, will be most readily understood by imagining the very reverse of that which is vulgarly attributed to Locke; viz., by draw ing a strong and well•marked line between the province of thought and that of sensation in the production of ideas, and taking care that, in the process of forming conceptions, the mind shall always stand out as the dominant factor. In other words, the hack neyed simile of the sheet of blank paper, applied to the mind by extreme sensational philosophers, must either he thrown away altogether or inverted; the more active part of the operation must always be assigned 16 the mind. The formation of knowledge, according to Plato, may be looked on as the gradual and systematic elimination of the accidental and ficettng in the phenomenon from the necessary and permanent; and the process by which the mind performs this elimination—and it can be performed only by mind—is called dialectics. This word, from dialegontoi, originally signifies only conver sational discussion; thence. that discussion conducted in such scientific fashion as to lead to reliable results, i.e., strictly logical. The product of dialectics is ideas. and these ideas being the forms or types of things which are common to all the individuals of a species, all the species of a genus, all the genera of a family, and till the families of a class, generate classification—that is, knowledge of the permanent in phenomena—and definition, which is merely the articulate verbal expression of this permanency. The construction of the confused resttlts of observation into the orderly army of clear con ceptions, by a sort of cross-examination of the phenomena, performed by minds impas sioned for truth, is exhibited as the great characteristic of the teaching of Socrates, in the Ihremorabilia of Xenophon. In the dialogues of Plato, the same purification of the reason, so to speak, from the clouds of indistinct sensuousness, is exhibited on a higher platform. and with more comprehensive results. For between Socrates and Plato, notwithstand ing, a deep internal identity, there was this striking difference in ontward attitude—that the one used logic as a practical instrument in the hands of a great social misSionaryand preacher of virtue; while the other used it as the architect of a great intellectual system of the universe, first and chiefly for his own time and his own place; but, as the event has proved, in some fashion also for all times and all places.
We should err greatly, however, if we looked on Plato as a man of there speculation, and-a writer of metaphysical books, like Certain German professors. Neither Plato nor any of the great Greeks looked on their intellectual exercises and recreations as an end in themselves. With them, philosophy did not mean mere knowledge or mere speculation, but it meant wisdom, and wisdom meant wise action, and wise action meant virtue. The philosophy of Plato, therefore, with all its transcendental flights, of which we hear so much, was essentially a practical philosophy; all his discussions on the theory of knowl edge and the nature of ideas are undertaken mainly that a system of eternal divine types, as the only reliable knowledge, may serve as a foundation for a virtuous life, tis the only consistent course of action. Virtue, with Socrates and Plato, is only practical reason. As in the Proverbs of Solomon, all vice is folly, so in the philosophy of Plato, the imperial virtue is "wisdom" or practical "insight." The other two great Greek
and Platonic "moderation" or "sound-mindedness," and dikaiosyne, "justice." or the assigning to every act and every function its proper place—are equally exemplifications of a reasonable order applied to action—such an order as alone and everywhere testifies the presence of mind. The theory of morals as worked out from such principles is, of course, as certain as the necessary laws of the reason which it expresses; and accordingly, the Platonic morality, like the Christian, is of that high order which admits of no compromise with ephemeral prejudice or local usage. The contrast between the low moral standard of local respectability and that which is con gruous with the universal laws of pure reason, stands out as strikingly in Plato as the morality of the Sermon on the Mount -in the Gospels does against the morality of the Scribes and Pharisees. Splendid passages to this effect occurs in various parts of Plato's writings, particularly in the Republic and the Gorgias. In perfect harmony with the Platonic theory of noble action, is his doctrine with regard to pure emotion and elevated passion. Love with Plato is a transcendental admiration of excellence—an admiration of which the soul is capable by its own high origination and the germs of god-like excel lence, which are implanted into it from above. The philosophy of love is set forth with imaginative grandeur in the P/ardne8, and with rich dramatic variety in the Banquet, of which dialogue there is an English translation by Shelley. The philosophy of beauty and .the theory of pleasure are sat forth with great analytic acuteness in the Philebus. With Plato, the foundation of beauty is a reasonable order, addressed to the imagination through the senses—i.e., symmetry in form, and harmony in sounds, the principles of which are as certain as the laws of logic, mathematics, and morals—all signally neces sary products of eternal intellect, acting by the creation and by the comprehension of well-ordered forms, and well-harmonized forces. in rich and various play through the living frame of the universe; and the ultimate ground of this lofty and coherent doctrine of intellectual, moral, and msthetieal harmonies lies with Plato, where alone it can lie, in the unity of a supreme, reasonable, self-existent intelligence, whom we call God, the fountain of all force, and the creator of all order in the universe; the sum of whose most exalted attributes, and the substantial essence of whose perfection con trasted with our finite and partial aspects of things, be expressed by the simple term td Good. From this supreme and alt-excellent intelligence, human souls are offshoots, emanations, or sparks, in such a fashion that they partake essentially of the essential nature of the source from which they proceed, and accordingly possess unity its their most characteristic quality, attest their presence everywhere by a unifying force which acts by impressing a type on whatever materials are submitted to it, and is filled with a native joy in the perception of such types, the product of the same divine' prin ciple of unity, wheresoever presented. The undivided unity and unifying force which we call the soul is immortal, being from its nature altogether unaffected by the changes of decay and dissolution to which the complex structure of the material human body is exposed. The doctrine of the immortality of the soul is most fully set forth in the Pieced°, a dialogue which combines with the abstract philo 3ophical discussion a graphic narrative of the last hours of Socrates, which, for simple athos and unaffected dignity, Is unsurpassed by any human composition.