Since we hold that the great God is in essence simple, invisible, and incorporeal, Himself pure intelligence, or something transcending intelligence and existence, we can never say that God is apprehended by any other means than through the intelligence which is formed in His image, though now, in the words of Paul, “we see in a glass obscurely, but then face to face.” And if we use the expression “face to face,” let no one pervert its meaning; but let it be explained by this passage, “Beholding with open face the glory of the Lord, we are changed into the same image, from glory to glory,” which shows that we do not use the word in this connection to mean the visible face, but take it figuratively, in the same way as we have shown that the eyes, the ears, and the other parts of the body are employed.
And it is certain that a man— I mean a soul using a body, otherwise called “the inner man,” or simply “the soul”— would answer, not as Celsus makes us answer, but as the man of God himself teaches. It is certain also that a Christian will not make use of “the language of the flesh,” having learned as he has “to mortify the deeds of the body” by the spirit, and “to bear about in his body the dying of Jesus;” and “mortify your members which are on the earth,” and with a true knowledge of these words, “My spirit shall not always strive with man, for that he also is flesh,” and again, “They that are in the flesh cannot please God,” he strives in every way to live no longer according to the flesh, but only according to the Spirit.
Source: Against Celsus (New Advent)