Because "early man demand[ed] of his serious epic poetry that it speak the truth
it follows that, since the epics are made up of myths, we must conclude that these myths, apparently even in their detail, were accepted as reality." This comes from the idea that in both the pre- and post-Homeric periods, "poetry was not apart from religion, but the essential medium of human knowledge about the gods." The Greeks believed that their poets were divinely inspired by the gods, and in particular by the Museshence the ubiquitous invocations of the Muses at the beginnings of poetic works.Moreover, the poets were granted automatic veracity not only through their inspirational contact with the gods but also because the Greeks believed that one cannot lie ex nihilo:in every lie there must be some element of truth, however small or distorted. Therefore, the poets, especially Homer, could not have simply made up the tales they told, for it was impossible, according to the Greeks, to fabricate stories in that fashion.
As a result the Homeric epics were regarded as truthful, and this was as true of the gods' anthropomorphism as of any other aspect of the poems.One can see this in the plentiful amounts of sculpture and pottery from the seventh to the fifth centuries that depict the gods in Homeric human forms. Furthermore, there is abundant evidence in the oral poetry of the Ionic period, which includes Hesiod, as well as in the Homeric Hymns and in the poetic traditions of the archaic lyric (the period in which Xenophanes wrote), that "all shared the basic Homeric conception of the gods."
However, it was this same Homeric tradition of anthropomorphic, human-like gods that Xenophanes criticized in his poetry:
Homer and Hesiod laid upon the gods all the things
that are faults and flaws with men:
stealing and adultery and cheating one another.
Previously, people for the most part had believed that one cannot measure the gods' actions against a human standard of morality, and that therefore their flagrant immorality was simply another aspect of their remoteness from mortals. But Xenophanes found the idea that the gods would behave in a human way at all simply ridiculous. He believed that humans of necessity view all things through the lens of their personal experience.
If the god had not created pale honey,
the figs would be said to be much sweeter.
In other words, humans base everything on their own knowledgeeverything is relative to their own conceptions of truth. Because of this, humans can never attain complete certainty about anything:
Concerning the gods and whatever I say about anything,
no one has any certainty, nor ever will;
and if someone should happen to utter the absolute truth,
how would he know it? Seeming is present in everything.
It seemed clear to Xenophanes that Homer's descriptions of the gods could not be the absolute truth, since humans have no access to the absolute, and it was painfully obvious to him that Homer and his fellow Greeks had merely modeled his gods on their own experiencesthey were human beings, therefore they made their gods have human forms.But it cannot follow that the gods therefore have human form in actuality.
If cows and horses or lions had hands
and made works of art like men,
the horses' gods would look like horses,
the cows' like cows; and they would model
the bodies of the gods upon their own.