II. In the Introductions to the Dialogues there have been added some essays on modern philosophy, and on political and social life. The chief subjects discussed in these are Utility, Communism, the Kantian and Hegelian philosophies, Psychology, and the Origin of Language. (There have been added also in the Third Edition remarks on other subjects. A list of the most important of these additions is given at the end of this Preface.)Ancient and modern philosophy throw a light upon one another: but they should be compared, not confounded. Although the connexion between them is sometimes accidental, it is often real. The same questions are discussed by them under different conditions of language and civilization; but in some cases a mere word has survived, while nothing or hardly anything of the pre-Socratic, Platonic, or Aristotelian meaning is retained. There are other questions familiar to the moderns, which have no place in ancient philosophy. The world has grown older in two thousand years, and has enlarged its stock of ideas and methods of reasoning. Yet the germ of modern thought is found in ancient, and we may claim to have inherited, notwithstanding many accidents of time and place, the spirit of Greek philosophy. There is, however, no continuous growth of the one into the other, but a new beginning, partly artificial, partly arising out of the questionings of the mind itself, and also receiving a stimulus from the study of ancient writings.
Considering the great and fundamental differences which exist in ancient and modern philosophy, it seems best that we should at first study them separately, and seek for the interpretation of either, especially of the ancient, from itself only, comparing the same author with himself and with his contemporaries, and with the general state of thought and feeling prevalent in his age. Afterwards comes the remoter light which they cast on one another. We begin to feel that the ancients had the same thoughts as ourselves, the same difficulties which characterize all periods of transition, almost the same opposition between science and religion.
Although we cannot maintain that ancient and modern philosophy are one and continuous (as has been affirmed with more truth respecting ancient and modern history), for they are separated by an interval of a thousand years, yet they seem to recur in a sort of cycle, and we are surprised to find that the new is ever old, and that the teaching of the past has still a meaning for us.
III. In the preface to the first edition I expressed a strong opinion at variance with Mr. Grote's, that the so-called Epistles of Plato were spurious. His friend and editor, Professor Bain, thinks that I ought to give the reasons why I differ from so eminent an authority. Reserving the fuller discussion of the question for another place, I will shortly defend my opinion by the following arguments:--(a) Because almost all epistles purporting to be of the classical age of Greek literature are forgeries. (Compare Bentley's Works (Dyce's Edition).) Of all documents this class are the least likely to be preserved and the most likely to be invented. The ancient world swarmed with them; the great libraries stimulated the demand for them; and at a time when there was no regular publication of books, they easily crept into the world.
(b) When one epistle out of a number is spurious, the remainder of the series cannot be admitted to be genuine, unless there be some independent ground for thinking them so: when all but one are spurious, overwhelming evidence is required of the genuineness of the one: when they are all similar in style or motive, like witnesses who agree in the same tale, they stand or fall together. But no one, not even Mr. Grote, would maintain that all the Epistles of Plato are genuine, and very few critics think that more than one of them is so. And they are clearly all written from the same motive, whether serious or only literary. Nor is there an example in Greek antiquity of a series of Epistles, continuous and yet coinciding with a succession of events extending over a great number of years.
