Celsus, not observing the difference between “after the image of God” and “God's image,” next asserts that the “first-born of every creature” is the image of God—the very word and truth, and also the very wisdom, being the image of His goodness, while man has been created after the image of God; moreover, that every man whose head is Christ is the image and glory of God—and further, not observing to which of the characteristics of humanity the expression “after the image of God” belongs, and that it consists in a nature which never had nor longer has “the old man with his deeds,” being called “after the image of Him who created it,” from its not possessing these qualities,— he maintains: “Neither did He make man His image; for God is not such an one, nor like any other species of (visible) being.”
Is it possible to suppose that the element which is “after the image of God” should exist in the inferior part— I mean the body— of a compound being like man, because Celsus has explained that to be made after the image of God? For if that which is “after the image of God” be in the body only, the better part, the soul, has been deprived of that which is “after His image,” and this (distinction) exists in the corruptible body—an assertion which is made by none of us. But if that which is “after the image of God” be in both together, then God must necessarily be a compound being, and consist, as it were, of soul and body, in order that the element which is “after God's image,” the better part, may be in the soul; while the inferior part, and that which “is according to the body,” may be in the body—an assertion, again, which is made by none of us.
It remains, therefore, that that which is “after the image of God” must be understood to be in our “inner man,” which is also renewed, and whose nature it is to be “after the image of Him who created it,” when a man becomes “perfect,” as “our Father in heaven is perfect,” and hears the command, “Be holy, for I the Lord your God am holy,” and learning the precept, “Be followers of God,” receives into his virtuous soul the traits of God's image. The body, moreover, of him who possesses such a soul is a temple of God; and in the soul God dwells, because it has been made after His image.
Source: Against Celsus (New Advent)