All the saints are lights, because by believing they are enlightened by him, to separate from whom will be to become dark. The light by which they are enlightened cannot become separated from itself because it is utterly unchangeable. So we believe an enlightened light, a prophet, say, or an apostle, but we believe them in such a way that we do not believe in the one who is enlightened but rather with him we believe in the light by which he is enlightened so that we too are enlightened, not by him, but, with him, by the same light as he. (In Ioannem Tr. 54, 4; PL 35, 1782)