Some scholars have denied altogether the possibility of pagan monotheism (e.g., Edwards 2000) in response to the recent interest (e.g. Frede 1999 and 2010). One objection is that “monotheistic” authors also believed in other supernatural beings (see, e.g., Versnel 2011, 239-308, on Xenophanes). Another objection is the lack of cult to a monotheistic God. The first objection, taken strictly, would rule out Judaism and Christianity, which admit lesser spiritual beings (Hurtado 1998, 27). Historical authors generally refer to “the divine” (to theion) or “the supernatural” (to daimonion) rather than simply “God.” They might say “the gods” to refer to supernatural intervention in events, but normally avoid attributing these to individual gods as in Homer. The paradox of simultaneous polytheism and monotheism may due to tradition or a kind of compartmentalization.
The necessity of a cult to qualify one as monotheist is also debatable. The Stoics, believed in a God identifiable with the logos or hegemonkon (reason or leading principle) of the universe (Sedley 2002) and downgraded the traditional gods, who even disappear during the conflagration (ekpyrosis). Yet, the Stoics apparently did not practice a cult to this God. Middle and Later Platonist, who spoke of a supreme God (cf., Bonazzi 2007, Cerutti 2010, Chaniotis 2010, North 2011, Van Nuffelen 2011), in philosophical discourse, generally speak of this God, not the gods, as responsible for the creation and providence of the universe. They, too, however, do not seem to have directly practiced a religious cult to their God.
There are a few examples, however, which go against this general rule. First, there is the cult of Theos or Zeus Hypsistos, described by John North as a “pagan vision” of Judaism (North 2011, 140). Many worshippers were pagans in a non-Jewish cult and worshipped a “highest,” supreme, monotheistic God quite unlike any traditional god (Mitchell 1999 and 2010, Belayche 2011). In Plutarch’s On the E at Delphi, the last and most impressive speaker, his teacher, Ammonius, equates God with Being (to on) and describes him as living in instant eternity, ruling and conserving the world with his providence, much like Philo of Alexandria (Whittaker 1969, Donini 1986, Dillon 2002, Ferrari 2005, Hirsch-Luipold 2005, Opsomer 2009, Brenk 2012, Thum 2013, Obsieger 2013). The setting is a religious shrine, Delphi, and a religious question is posed, the meaning of the “E” erected there. For Ammonius, the traditional Apollo is only a faint image of the real God. Even if Ammonius is not very explicit, the worshippers are to direct their cult, at least indirectly, to the real God, described in Middle Platonic terms. In On Isis and Osiris, Osiris also is only an image of the true God, identified with Plato’s Good and Beautiful, and as the destiny of the soul. This God, too, providentially rules the world through his powers (dynameis) (377F-378A) as in Philo (see Mackie 2009), presumably through or including the traditional gods. For Plutarch, then, the myth of Isis and Osiris is only an allegory masking a Middle Platonic conception of the universe and a Middle Platonic God. The Theos Hypsistos religion, then, though apparently influenced by Judaism, offers an example of cult. In the two works of Plutarch, even if they are more theoretical than practical, there are cultic ramifications. In any case, the examples reveal the existence of Graeco-Romans believing in and worshipping a monotheistic god and, in the second case, a Greek author, who is also a polytheist, in a cultic situation, apparently directing his readers to transform a traditional cult into a monotheistic one.
“Theism” and Related Categories in the Study of Ancient Religions