According to the standard view, the religious culture of the Graeco-Roman world was polytheistic. Men and women worshipped an enormous variety of gods, goddesses and divine beings, and their beliefs were integrated by various cultural mechanisms (language, sacrificial rituals, generally agreed notions about where the dividing line between the secular and sacred was situated) into a common religious system. Graeco-Roman paganism (to use the convenient label) thus contrasted strongly with monotheistic religious systems, notably Judaism and its offspring, Christianity.
2. The evidence for pagan monotheism
Monotheistic beliefs were nevertheless widespread and influential throughout the ancient world in the Hellenistic and Roman Imperial Periods, especially in the eastern Mediterranean and the Near East. Greek philosophers had envisaged the existence of a single divine being as early as the sixth century BC. Belief in a ‘Highest God’ can be traced at all levels of society across the eastern Mediterranean and the adjacent areas of the Balkans, Ukraine, South Russia, Anatolia, the Near East and Egypt, beginning about 300 BC. Strict monotheism, which denied divine status for any but the one god, was relatively rare, but various forms of ‘soft monotheism’ or henotheism, which allowed subordinate status to angels or lesser divinities beneath an omnipotent deity, were widespread. Moreover, there was a considerable body of theological literature which tried to define the relationship between the supreme being and the lesser divinities of traditional paganism. In the later Roman Period from the 2nd century AD onwards such beliefs were considerably influenced by the increasingly dominant monotheistic systems of Judaism and Christianity. The evidence for pagan monotheism has been so overshadowed by these, that it has passed largely unnoticed.
3. Current research
This phenomenon has been widely observed but rarely subjected to systematic historical investigation or explanation. A recent exception is G. Fowden’s stimulating short book, From Empire to Commonwealth. The Consequences of Monotheism in Late Antiquity (1993). His fundamental approach is to correlate changes in religious outlook with changes in the political culture and patterns of authority in the later Roman and Sassanian Empires. An alternative approach is to explore the reasons for and circumstances of this remarkable transformation of religious norms by an examination of the precise historical contexts that generated new religious developments, and to interpret religious and social change from the bottom up, and not as a reflection of large-scale political systems.
4. Evidence for monotheism in Asia Minor
Asia Minor has provided a substantial quantity of evidence for monotheistic or henotheistic cults. The most important of these was the cult of "Theos Hypsistos" (less often Zeus Hypsistos), the Highest God, attested by about 300 inscriptions from Asia Minor and the adjoining regions between the 2nd century BC and the 4th century AD. Theos Hypsistos was an abstract deity, never represented by a human image in pictorial form. Most of the inscriptions are ordinary dedications set up by humble people, although there is also evidence that the god was worshipped by people from higher social levels. Followers of the cult in the fourth century were known to Christian writers as Hypsistarii or Hypsistiani, and they explain that their beliefs consisted in a mixture of Greek pagan and Jewish rites,1 but also came close in some respects to Christianity. Epiphanius, the fourth century bishop of Salamis in Cyprus, described their rituals, which included the use of lamps, cultic acclamations and the singing of hymns.2 They often worshipped in open-air sanctuaries, one of which has been identified at the city of Oenoanda in Lycia. Another was the cult site of "Zeus Hypsistos" or "Hypsistos" on the Pnyx in Athens. In addition, many followers of the cult joined Jews in worshipping "Theos Hypsistos in synagogues". Another patristic source, Cyril of Alexandria, tells us that they called themselves "theosebeis", ‘god-fearers’.3 This is the term used by Josephos and the author of the Acts of the Apostles to describe non-Jewish worshippers who worshipped in Jewish synagogues in the 1st century AD, and there is good reason to believe that the worshippers of "Theos Hypsistos" and the "God-Fearers" were identical. This indicates that there was a considerable degree of common ground between the beliefs of the Jews of the Diaspora and those of the Hypsistarians, and also that Christian and Hypsistarian beliefs and practices could be very similar.
5. The written testimony
The most succinct expression of their beliefs is provided by an oracle of Clarian Apollo, given in response to the question ‘who is god?’ This text was well known in Late Antiquity and cited by Christian authors. More importantly it is known from an inscription of the third century AD, which was found in the sanctuary of Theos Hypsistos at Oenoanda in Lycia:4
‘Born of itself, untaught, without a mother, unshakeable, not contained in a name, known by many names, dwelling in fire, this is god. We, his angels, are a small part of god. To you who ask this question about god, what his essential nature is, he has pronounced the aether is god who sees all, on whom you should gaze and pray at dawn, looking towards the sunrise.’
It is evident from this text that adoration of the sun was another feature of this form of monotheistic belief, and also that other heavenly beings, including Apollo who delivered this oracle, were to be regarded not as gods but as angels. The cult of pagan angels is well attested in Lydia, Caria and Phrygia.
Today’s dominant monotheistic religious systems, Judaism, Christianity and Islam, had their origins in the Roman Imperial Period. One of the remarkable features of these religious systems was the speed with which they spread and established themselves outside their regions of origin. The monotheistic conceptions of the cult of "Theos Hypsistos" were a seedbed into which Jewish and Christian theology could readily be planted, and the popularity of the cult helps to explain why the latter spread so rapidly.