The Hymn to Zeus of Cleanthes, second head of the Stoa in the third century BCE, is the one substantial piece of early Stoic writing to survive intact, preserved by the anthologist Stobaeus, and the clearest statement of Stoic theology in poetic form. Its Zeus is not the philandering god of the myths but the rational principle (logos) that orders the cosmos: the universal reason and law through which all things come to be and are governed, addressed with genuine religious feeling as the one whom it is right for mortals to praise.
What gives the hymn its interest is that it is a real prayer built on a philosophical theology. Cleanthes asks Zeus to free human beings from the ignorance that makes them go wrong, and he confronts directly the problem of evil: nothing happens on earth apart from the divine reason except what the wicked do in their folly, yet even that God fits into the order of the whole. The poem thus holds together a rigorous determinism and a call to virtue, and it stands near the head of a long tradition, running through the Roman Stoics and into later monotheist thought, of addressing the ordering principle of the universe in the language of worship.
The hymn survives only because Stobaeus, compiling an anthology of Greek verse in late antiquity, chose to preserve it entire, a reminder of how much early Stoic writing is otherwise lost and known only through later summary. Its closing plea, that mortals be granted a share in the reason that governs the universe, has often been read alongside a nearby line from Aratus on humanity as the offspring of God, quoted in Acts, as evidence of how directly Stoic religious language fed into early Christian and later monotheist vocabulary for addressing a single ordering God.