In Plato, the disciple and exponent of Socrates, Greek speculation may be said to have reached its culminating point. How greatly his thoughts have influenced the course of philosophy in subsequent times, even to our own day, may be judged from the following words of the late Professor Jowett in his introduction to the _Republic_, which is generally acknowledged to be the greatest and most suggestive of the numerous works of Plato:-- “He (Plato) was the greatest metaphysical genius whom the world has seen; and in him, more than in any other ancient thinker, the germs of future knowledge are contained. The sciences of logic and psychology, which have supplied so many instruments of thought to after-ages, are based on the analyses of Socrates and Plato. The principles of definition, the law of contradiction, the fallacy of arguing in a circle, the distinction between the essence and accidents of a thing or notion, between means and ends, between causes and conditions; also the division of the mind into the rational, concupiscent and irascible elements, or of pleasures and desires into necessary and unnecessary--these and other great forms of thought are all of them to be found in the _Republic_, and were probably first invented by Plato. The greatest of all logical truths, and the one of which writers on philosophy are most apt to lose sight, the difference between words and things, has been most strenuously insisted on by him.... In the _Republic_ is to be found the original of Cicero’s _De Republica_, of St. Augustine’s _City of God_, of the _Utopia_ of Sir Thomas More, and of the numerous other States which are framed upon the same model.... The _Republic_ of Plato is also the first treatise upon education, of which the writings of Milton and Locke, Rousseau, Jean Paul, and Goethe are the legitimate descendants. Like Dante or Bunyan, he has a revelation of another life; like Bacon, he is profoundly impressed with the unity of knowledge; in the early Church he exercised a real influence on theology, and at the revival of literature on politics.... He is the father of idealism in philosophy, in politics, in literature; and many of the latest conceptions of modern thinkers and statesmen, such as the unity of knowledge, the reign of law, and the equality of the sexes, have been anticipated in a dream by him.” CHAPTER XII ATHENS--ITS DECAY AND ITS REVIVAL