Monotheism

===Europe===
====Ancient proto-Indo-European religion====
{{main|Proto-Indo-European religion}}
The head deity of the [[Proto-Indo-European religion]] was the god [[Dyeus|*''Dyḗus Pḥ<sub>a</sub>tḗr '']]. A number of words derived from the name of this prominent deity are used in various [[Indo-European languages]] to denote a monotheistic God. Nonetheless, in spite of this, Proto-Indo-European religion itself was not monotheistic.<ref>{{cite book|last1=Mallory|first1=J. P.|last2=Adams|first2=D.Q.|title=The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World|date=2006|publisher=Oxford University Press|location=Oxford, England|isbn=978-0-19-929668-2|pages=408–411 and 423–434}}</ref>

In [[Eastern Europe]], the ancient traditions of the Slavic religion contained elements of monotheism. In the sixth century AD, the Byzantine chronicler [[Procopius]] recorded that the Slavs "acknowledge that one god, creator of lightning, is the only lord of all: to him do they sacrifice an ox and all sacrificial animals."<ref name=katicic2008>{{cite book |last=Katičić |first=Radoslav |title=Božanski boj: Tragovima svetih pjesama naše pretkršćanske starine |year=2008 |publisher=IBIS GRAFIKA |location=Zagreb |isbn=978-953-6927-41-8 |url=http://ir.nmu.org.ua/bitstream/handle/123456789/120570/96db5654f2d3025b46454ace91716506.pdf |ref=Katičić 2008 |url-status=dead |archive-url=https://web.archive.org/web/20151018000746/http://ir.nmu.org.ua/bitstream/handle/123456789/120570/96db5654f2d3025b46454ace91716506.pdf |archive-date=2015-10-18 }}</ref> The deity to whom Procopius is referring is the storm god [[Perún]], whose name is derived from [[Perkwunos|*''Perk<sup>w</sup>unos'']], the Proto-Indo-European god of lightning. The ancient Slavs syncretized him with the Germanic god [[Thor]] and the Biblical prophet [[Elijah]].<ref>{{citation|last1=Puhvel|first1=Jaan|author-link=Jaan Puhvel|title=Comparative Mythology|date=1987|publisher=Johns Hopkins University Press|location=Baltimore, Maryland|isbn=0-8018-3938-6|pages=234–235}}</ref>

====Ancient Greek religion====
{{main|Ancient Greek religion}}

=====Classical Greece=====
[[File:Xenophanes in Thomas Stanley History of Philosophy.jpg|thumb|upright=0.7|Fictionalized portrait of [[Xenophanes]] from a 17th-century engraving]]
The surviving fragments of the poems of the classical Greek philosopher [[Xenophanes of Colophon]] suggest that he held views very similar to those of modern monotheists.<ref>McKirahan, Richard D. "Xenophanes of Colophon. ''Philosophy Before Socrates''. Indianapolis: Hackett Publishing Company, 1994. 61. Print.</ref> His poems harshly criticize the traditional notion of anthropomorphic gods, commenting that "...if cattle and horses and lions had hands or could paint with their hands and create works such as men do,... [they] also would depict the gods' shapes and make their bodies of such a sort as the form they themselves have."<ref>Diels-Kranz, ''Die Fragmente der Vorsokratiker'', Xenophanes frr. 15-16.</ref> Instead, Xenophanes declares that there is "...one god, greatest among gods and humans, like mortals neither in form nor in thought."<ref name="osborne62">Osborne, Catherine. "Chapter 4." ''Presocratic Philosophy: A Very Short Introduction''. Oxford UP. 62. Print.</ref> Xenophanes's theology appears to have been monist, but not truly monotheistic in the strictest sense.<ref name="auto" /> Although some later philosophers, such as [[Antisthenes]], believed in doctrines similar to those expounded by Xenophanes, his ideas do not appear to have become widely popular.<ref name="auto" />

Although [[Plato]] himself was a polytheist, in his writings, he often presents [[Socrates]] as speaking of "the god" in the singular form. He does, however, often speak of the gods in the plural form as well. The [[Euthyphro dilemma]], for example, is formulated as "Is that which is holy loved by the gods because it is holy, or is it holy because it is loved by the gods?"<ref>{{cite web|last1=Lamb|first1=W. R. M.|title=Euthyphro|url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0170%3Atext%3DEuthyph.%3Asection%3D10a|website=Perseus|publisher=Tufts University|access-date=25 March 2017|archive-date=23 August 2015|archive-url=https://web.archive.org/web/20150823015053/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0170%3Atext%3DEuthyph.%3Asection%3D10a|url-status=live}}</ref>

=====Hellenistic religion=====
{{main|Hellenistic religion}}
The development of pure (philosophical) monotheism is a product of the [[Late Antiquity]]. During the 2nd to 3rd centuries, [[origins of Christianity|early Christianity]] was just one of several competing religious movements advocating monotheism.

"[[Henology|The One]]" ({{lang|el|Τὸ Ἕν}}) is a concept that is prominent in the writings of the [[Neoplatonists]], especially those of the philosopher [[Plotinus]].<ref>{{cite book|last1=Wyller|first1=Egil A.|title=Henologische Perspektiven II: zu Ehren Egil A. Wyller, Internales Henologie-Symposium|date=1997|publisher=Rodopi|location=Amsterdam, Netherlands|isbn=90-420-0357-X|pages=5–6|url=https://books.google.com/books?id=QbMAMtaJWIIC&q=Henology&pg=PA5|access-date=25 March 2017}}</ref> In the writings of Plotinus, "The One" is described as an inconceivable, transcendent, all-embodying, permanent, eternal, causative entity that permeates throughout all of existence.<ref>{{cite book|last1=Schürmann|first1=Reiner|last2=Lily|first2=Reginald|title=Broken Hegemonies|date=2003|publisher=Indiana University Press|location=Bloomington, Indiana|isbn=0-253-34144-2|pages=143–144|url=https://books.google.com/books?id=4eRv1DTW_KoC&q=Henology&pg=PA109|access-date=25 March 2017}}</ref>
[[File:Columns of the Temple of Apollo at Delphi, Greece.jpeg|thumb|Remains of the [[Temple of Apollo (Delphi)|Temple of Apollo]] at Delphi, Greece]]

A number of oracles of [[Apollo]] from [[Didyma]] and [[Clarus]], the so-called "theological oracles", dated to the 2nd and 3rd century CE, proclaim that there is only one highest god, of whom the gods of polytheistic religions are mere manifestations or servants.<ref>[[Dictionary of Deities and Demons in the Bible]], s.v. "Apollo".</ref> 4th century CE Cyprus had, besides Christianity, an apparently monotheistic cult of [[Dionysus]].<ref>E. Kessler, ''Dionysian Monotheism in Nea Paphos, Cyprus'': "two monotheistic religions, Dionysian and Christian, existed contemporaneously in Nea Paphos during the 4th century C.E. [...] the particular iconography of Hermes and Dionysos in the panel of the Epiphany of Dionysos [...] represents the culmination of a pagan iconographic tradition in which an infant divinity is seated on the lap of another divine figure; this pagan motif was appropriated by early Christian artists and developed into the standardized icon of the Virgin and Child. Thus the mosaic helps to substantiate the existence of pagan monotheism." [([http://www.huss.ex.ac.uk/classics/conferences/pagan_monotheism/abstracts.html Abstract] {{webarchive|url=https://web.archive.org/web/20080421032154/http://www.huss.ex.ac.uk/classics/conferences/pagan_monotheism/abstracts.html |date=2008-04-21 }})</ref>

The [[Hypsistarian]]s were a religious group who believed in a most high god, according to Greek documents. Later revisions of this Hellenic religion were adjusted towards monotheism as it gained consideration among a wider populace. The worship of Zeus as the head-god signaled a trend in the direction of monotheism, with less honour paid to the fragmented powers of the lesser gods.