exact thinking requires. Even when we speak of method we are using an Aristotelian term, and when we distinguish one subject from another we are employing the Latin translation of the word which Aristotle introduced. In a word, modern thought, scientific and philosophic alike, has a unitary origin. It is derived from the Greek. The mode of this derivation is not simple, and would require considerable space to examine in detail. In outline it must suffice to say that the Greek culture was spread over the Eastern Mediterranean through the conquests of Alexander, and that as its capital Alexandria gradually replaced Athens. It flowed westward with the Roman conquests, when, as the Roman poet said, captured Greece took captive her barbarous conqueror and introduced the arts into rustic Latium. It shared in the general decline which accompanied the rebarbarization and final collapse of the Roman Empire. But now occurred a division in the stream of historic tendency. The fortunes of East and West were separated. The Western Empire was overrun by Germanic tribes, and after the sixth century the tradition of the old culture was maintained for the most part in the monasteries. Greek was forgotten in the West. Greek authors were known only in Latin translations, and science and philosophy came to a standstill. In the East the Mohammedan conquests brought the Arabs into touch with Greek learning. They preserved the tradition and extended the work, and it was the contact with Arabic culture through the crusades which initiated the first renaissance in the West in the twelfth century. There followed the epoch of the great mediaeval systems, the rediscovery of Aristotle and the attempt to fuse the Christian faith with the Aristotelian system. The later Middle Age was the period at which Western civilization was most distinctly a cultural unit, the scene of a great attempt to unify all the aspects of life, the religious, the philosophic, the political, on the basis of a religious faith made articulate and systematic with the aid of Greek philosophy, speaking the Latin tongue as the common possession of all educated men.