Previous to Aristotle, Greek thought had been wonderfully free and elastic. It had not settled into compartments or assumed an educational form which would secure its unrevised transmission from teacher to student. It was not gathered together in systematic treatises. Aristotle combined the supreme powers of an original and creative thinker with the impulses of a textbook writer. He loved order and classification. He supplied manuals of Ethics, Politics, Logic, Psychology, Physics, Metaphysics, Economics, Poetics, Zoölogy, Meteorology, Constitutional Law, and God only knows what not, for we do not have by any means all the things he wrote. And he was equally interested, and perhaps equally capable, in all the widely scattered fields in which he labored. And some of his manuals were so overwhelming in the conclusiveness of their reasoning, so all-embracing in their scope, that the mediaeval universities may be forgiven for having made them the sole basis of a liberal education and for imposing fines on those who ventured to differ from "The Philosopher". He seemed to know everything that could be known and to have ordered all earthly knowledge in an inspired codification which would stand the professors in good stead down to the day of judgment. Aristotle combined an essentially metaphysical taste with a preternatural power of observation in dealing with the workings of nature. In spite of his inevitable mistakes, which became the curse of later docile generations, no other thinker of whom we have record can really compare with him in the distinction and variety of his achievements. It is not his fault that posterity used his works to hamper further progress and clarification. He is the father of book knowledge and the grandfather of the commentator. After two or three hundred years of talking in the market place and of philosophic discussions prolonged until morning, such of the Greeks as were predisposed to speculation had thought all the thoughts and uttered all the criticisms of commonly accepted beliefs and of one another that could by any possibility occur to those who had little inclination to fare forth and extend their knowledge of the so-called realities of nature by painful and specialized research and examination. This is to me the chief reason why, except for some advances in mathematics, astronomy, geography, and the refinements of scholarship, the glorious period of the Greek mind is commonly and rightfully assumed to have come to an end about the time of Aristotle's death. Why did the Greeks not go on, as modern scientists have gone on, with vistas of the unachieved still ahead of them?