=The Divisions of Ancient Philosophy.= The history of ancient philosophy falls naturally into two large divisions: pure Greek philosophy and Hellenic-Roman philosophy (or Greek philosophy in the Roman world). The date, 322 B. C., the death of Aristotle, which marks the line between these two periods, is one of the milestones of history. Alexander the Great had died in 323 B. C. The coincidence of the deaths of Aristotle and Alexander not only suggests their intimate relations as teacher and pupil during their lives, but it throws into contrast Greek civilization before and after them. Before Aristotle and Alexander culture was the product entirely of the pure Greek spirit; after them ancient culture was the complex product of many factors――of Greek and Roman civilizations, and many Oriental religions, including Christianity. Before Aristotle and Alexander, ancient culture was characterized by a love of knowledge for its own sake, by freedom from ulterior ends either of service or of use; after these great makers of history, culture became attenuated to work in the special sciences and enslaved to practical questions. Before Aristotle and Alexander, the Greek city-states had arisen to political power; after Aristotle and Alexander, Greece declined politically and was absorbed into the Roman empire. =The Literary Sources of Ancient Philosophy.[2]= The literary sources of ancient philosophy are three: (1) the primary sources, or original writings; (2) the secondary sources, or reports of the original writers obtained indirectly, or through other writers; (3) the interpretations of reliable modern historians of philosophy. The specialist in philosophy will, of course, go to the first two sources for his information. Other students will find many accurate modern histories of ancient philosophy. The student should have at hand the translations of the histories of Zeller, Windelband, Weber, Eucken, Ueberweg; those of the Englishmen, Burnet and Fairbanks; of the Americans, Rogers and Turner. “The writings of the early Greek philosophers of the pre-Socratic period exist now only in fragments. The complete works of Plato are still extant; so also are the most important works of Aristotle, and certain others which belong to the Stoic, Epicurean, Skeptic, and neo-Platonic schools. We possess the principal works of most of the philosophers of the Christian period in sufficient completeness.”[3] The secondary sources include quotations and comments upon earlier philosophers found in the writings of Plato, Aristotle, the Stoics, Skeptics, neo-Platonists, and the so-called doxographers. Doxography――the commentating upon and collating of the works of former times――developed enormously in Alexandria, Pergamos, and Rhodes just after Aristotle. The founder of this work was Theophrastus, who was a disciple of Aristotle and his successor in the Lyceum. Among the important doxographers were Plutarch, Stobæus, and Aetios.