Referring to the passage in the Phædon of Plato, Celsus says: “It is not easy for every one to understand the meaning of Plato's words, when he says that on account of our weakness and slowness we are unable to reach the highest region of the air; but that if our nature were capable of so sublime a contemplation, we would then be able to understand that that is the true heaven, and that the true light.” As Celsus has deferred to another opportunity the explanation of Plato's idea, we also think that it does not fall within our purpose at present to enter into any full description of that holy and good land, and of the city of God which is in it; but reserve the consideration of it for our Commentary on the Prophets, having already in part, according to our power, treated of the city of God in our remarks on Psalm 46 and Psalm 48.
The writings of Moses and the prophets— the most ancient of all books— teach us that all things here on earth which are in common use among men, have other things corresponding to them in name which are alone real. Thus, for instance, there is the true light, and another heaven beyond the firmament, and a Sun of righteousness other than the sun we see. In a word, to distinguish those things from the objects of sense, which have no true reality, they say of God that “His works are truth;” thus making a distinction between the works of God and the works of God's hands, which latter are of an inferior sort. Accordingly, God in Isaiah complains of men, that “they regard not the works of the Lord, nor consider the operation of His hands.” But enough on this point.
Source: Against Celsus (New Advent)