The Six Books of Proclus on the Theology of Plato, Volume 1

Again, from another principle we may be able to apprehend the theological demonstrations in the Republic. For these are common to all the divine orders, similarly extend to all the discussion about the Gods, and unfold to us truth in uninterrupted connexion with what has been before said. In the second book of the Republic therefore, Socrates describes certain theological types for mythological poets, and exhorts his pupils to purify themselves from those tragic disciplines, which some do not refuse to introduce to a divine nature, concealing in these as in veils the arcane mysteries concerning the Gods. Socrates therefore, as I have said, narrating the types and laws of divine fables, which afford this apparent meaning, and the inward concealed scope, which regards as its end the beautiful and the natural in the fictions about the Gods,—in the first place indeed, thinks fit to evince, according to our unperverted conception about the Gods and their goodness, that they are the suppliers of all good, but the causes of no evil to any being at any time. In the second place, he says that they are essentially immutable, and that they neither have various forms, deceiving and fascinating, nor are the authors of the greatest evil lying, in deeds or in words, or of error and folly. These therefore being two laws, the former has two conclusions, viz. that the Gods are not the causes of evils, and that they are the causes of all good.

The second law also in a similar manner has two other conclusions; and these are, that every divine nature is immutable, and is established pure from falsehood and artificial variety. All the things demonstrated therefore, depend on these three common conceptions about a divine nature, viz. on the conceptions about its goodness, immutability and truth. For the first and ineffable fountain of good is with the Gods; together with eternity, which is the cause of a power that has an invariable sameness of subsistence; and the first intellect which is beings themselves, and the truth which is in real beings.