Ionian and mainland Greece, which were to be the parents of Greek thought, were richly placed in that they had living contacts with some of the high cultures of the period, in the sixth and fifth centuries bce, when the first major stirrings of philosophy took place. The Persian empire to the east had, under Cyrus the Great, conquered most of Asia Minor, together with Babylonia and Media, by the year 630, when he was killed. It remained for his heir to bring Egypt into subjection. So most of the Middle East was unified, with cultural heritages tracing back to ancient Sumer and Babylon, Egyptian civilization and the traditions of the Persians themselves. Only certain elements of these cultures turned out to be important in the later history of ideas. First, Babylonian astronomy and Egyptian geometry were to some degree absorbed by the Greeks, who notably developed mathematics and especially geometry. Second, Zoroastrian ideas (which we shall describe later) not only influenced Judaism and through that Christianity, especially in regard to the figure of the Devil and in the belief in the resurrection of the dead, but they also had a strong presence in Manichaeanism, a once important faith which stretched from the Roman empire (and there had its effects upon Augustine) to China. Third, and most importantly, Jewish ideas made a strong impact on the world of the Roman empire, especially through the wide-ranging success of the new religious movement which came to be known as Christianity. Christian beliefs coalesced with those of Neoplatonism to constitute classical Christian doctrine. We shall deal with these influences upon later philosophies in the course of recounting the narrative of the development of Greek and Roman philosophy. The roots of Zoroastrian and Jewish ideas stretch back before the period of the rise of the first Greek speculations: but we shall nevertheless deal with them in the order of their impact upon the wider world, rather than strictly chronologically.