expression of beauty ever made by the human race. In the latter part of this period books, also, were in common use, although not as yet very numerous. Peisistratos had founded a library for those who applied themselves to letters, which had passed through various vicissitudes, and the Athenians had increased it with a great deal of care. To the stock of books in existence at that time Anaxagoras made an important addition. His book did not have an original title, being called πέρι φύσεμς, or 'On Nature,' like many other productions of Ionian philosophers, but his ideas were original, and it was the first book to be illustrated by diagrams, with the exception of geometrical writings. In Plato's time the book was on sale for a drachma, although it is said to have consisted of several volumes. Probably the volumes may have been rather what we should call chapters. This book, alas, is no longer in existence, although we possess important fragments of it, mostly found in Simplicius's commentary on Aristotle's physics, which was written in the sixth century, at which time a copy of the book was to be had.
Let us now consider some strange phenomena in connection with the first appearance of the idea of spirit in Greek philosophy. Anaxagoras himself had the characteristics of the idealist, but his world theory and the general trend of his studies were closely allied with the teachings of his materialistic predecessors in Ionia. He could not wholly escape from his age. When Sokrates heard of Anaxagoras's book he was delighted that some one had attributed the universe to an all-pervading spirit, and immediately sent for the book; but he was ;greatly disappointed on reading it, as he did not find there the idealism for which he had sought. Anaxagoras belonged not to the age of Sokrates, although he was partly contemporary with him, but he belonged wholly to the Ionian school of mathematical astronomy. The thought of Anaxagoras was scientific rather than philosophic, and his book was devoted to scientific, mathematical explanations of cosmography and astronomy. The Nous was not to him the all-important part, but only a necessary cause for the beginning of motion—a secondary first cause, so to speak. Yet the idea of the Nous was sufficient to introduce rationalism into Greece, for it was the first presentation of an existing rational force wholly distinct from matter. Anaxagoras was bent upon scientific discovery, and the important things in his mind were his method and his original theory of matter. How often it happens that what seems secondary to a great man proves after all his most far-reaching service to the world. As, for example, with Plato his philosophy was secondary in his own mind to his ideas of political reform, and, while it is true that the latter have been much regarded, yet the former have revolutionized all philosophic thought. Anaxagoras's rationalism did not enable him to produce a rational theory of matter, yet it rationalized all his thought and was a stepping
