Xenophanes was a pre-Socratic philosopher. He famously questioned the polytheism of the Greeks, saying that the gods were portrayed as acting immorally and that men made gods in their own likeness. It looks like he is groping towards a monotheistic view like the major religions hold today. Where he differs is in denying that men is made in Gods image.
πάντα θεοῖς ἀνέθηκαν Ὅμηρός θ᾽ Ἡσίοδός τε,
ὅσσα παρ᾽ ἀνθρώποισιν ὀνείδεα καὶ ψόγος ἐστίν,
κλέπτειν μοιχεύειν τε καὶ ἀλλήλους ἀπατεύειν.
Homer and Hesiod attributed to the gods all that is a shame and reproach among men, stealing and committing adultery and deceiving each other.
ἀλλ᾽ οἱ βροτοὶ δοκέουσι γεννᾶσθαι θεοὺς
τὴν σφετέρην ἐσθῆτατ᾽ ἔχειν φωνήν τε δέμας τε.
But men think that gods are born and have clothes and speech and bodies like ours.
εἰ δέ τοι ἵπποι ἔχον χέρας ἢ βόες ἠὲ λέοντες
ἢ γράψαι χροίῃσι καὶ ἔργα τελεῖν ἅπερ ἄνδρες,
καί κε θεῶν ἰδέας ἔγραφον καὶ σώματ᾽ ἐποίουν
τοιαῦθ᾽ οἷόνπερ καὐτοὶ δέμας εἶχον ἕκαστοι,
ἵπποι μέν θ᾽ ἵπποισι, βόες δέ τε βουσὶν ὁμοῖα.
But if horses or oxen or lions had hands or were able to draw and do the works men can do, they would draw the forms of the gods and make their bodies with the same appearance they themselves have; horses like horses and oxen like oxen.
Αἰθίοπές τε θεοὺς σφετέρους σιμοὺς μέλανάς τε
Θρῇκές τε γλαυκοὺς καὶ πυρρούς φασι πελέσθαι:
The Ethiopians say their gods are snub nosed and black and the Thracians their gods are blue eyed and red haired.
εἷς θεὸς ἔν τε θεοῖσι καὶ ἀνθρώποισι μέγιστος,
οὔ τι δέμας θνητοῖσιν ὁμοίϊος οὔτε νόημα.
There is one God, greatest among gods and men. He is like men neither in body or mind.
οὖλος ὁρᾷ, οὖλος δὲ νοεῖ, οῦλος δέ τ᾽ ἀκούει.
All of him sees, all thinks and all hears