Later attempts to study religion
Later Greek thinkers tended to vary between the positions adumbrated in the earlier period. The Stoics (philosophers of nature and morality) opted for a form of naturalistic monotheism, whereas the philosopher Epicurus (341–270 bce) was skeptical of religion as ordinarily understood and practiced, though he did not deny that there were gods who, however, had no transactions with human beings. Of considerable influence was Euhemerus (c. 330–c. 260 bce), who gave his name to the doctrine called Euhemerism—namely, that the gods are divinized humans. Although Euhemerus’s own argument was based largely upon fantasy, there are certainly some examples, both in Greek religion (e.g., Heracles) and elsewhere, of the tendency to make humans into gods, but it is obviously not universal.
Most of the Greek concepts about religion proved to be influential in the Roman world also. The atheistic Atomism of the Roman natural historian Lucretius (c. 95–55 bce) owed much to Epicurus. The eclectic thinker and politician Cicero (106–43 bce), in his De natura deorum (“Concerning the Nature of the Gods”), criticized Stoic, Epicurean, and later Platonic ideas about religion, but the book remains incomplete. Much of the skepticism about the gods in the ancient world was concerned with the older traditional religions, whether of Greece or Rome. But in the early empire the mystery cults, ranging from the Eleusinian mysteries of Greece to those of the Anatolian Cybele and the Persian Mithra, together with philosophically based religions such as Neoplatonism and Stoicism, had the greatest vitality. The patterns of religious belief were complex and of different levels, with various kinds of religion existing side by side.
Into this situation Christianity was injected, and in its encounter with classical civilization it absorbed a number of the critiques of the gods of the older thinkers. In particular, Euhemerism was fashionable among the Church Fathers (the religious teachers of the early church) as an account of paganism. On the “pagan” side, there were persistent attempts to justify the popular cults and myths by the extensive use of allegory—a technique well adapted to the synthesis of philosophical and popular religion. Christianity’s own contribution to theories of the genesis of polytheism was through the doctrine of the Fall of Man, in which pure monotheism was believed to have become overlaid by demonic cults of the gods. This account could help to explain some underlying similarities between the Jewish and Christian traditions on the one hand and the Greek and Roman traditions on the other. In this view lies the germ of an evolutionary account of religion. On the whole, however, the theories of religion in the ancient world were naturalistic and rationalist.