There exists in man an imperfect image of God; for the true conception of an image requires that it be taken from that of which it is the image. Hence an egg is not the image of another egg; it is only like it; but since there exists in man a certain likeness which is derived from God as Exemplar, he is said to be made to the image of God; not, however, according to any sort of equality; for the Exemplar infinitely transcends the example. Hence man is an imperfect image of God.
And this image is proper to intellectual creatures; for not every likeness which may find expression in another suffices for the conception of an image; as though in virtue of genus only a worm were to be likened to a man, or as things may resemble each other by some common accident, such as whiteness. The likeness must be according to species or to some accident proper to species; because resemblance is understood as relating to that which is most specific. Thus things resemble each other in the most general manner in virtue of their being; others more specifically in virtue of life; others in the most perfect manner, inasmuch as they know and understand.
Absolutely speaking, the angels are more to the image of God than man; according to that intellectual nature in which the primary conception of the image consists; relatively, however, the Divine image is found more in man, because man is from man as God is from God; also the human soul is entire in the whole body and in every part of it, as God is present relatively to the whole world. Thus in some respects the image of God is specially found in man, although the true conception of the image belongs properly to the intellectual nature.
This image of God, which is found in all men, may be considered under three aspects: first, as a natural aptitude for loving and understanding God, which belongs to the nature of the mind and is common to all men; secondly, as actual and habitual knowledge and imperfect love, which is the conformity of grace; and thirdly, as that perfect love and knowledge which constitute the image of God in a State of Glory. The first is in all men, the second in the just, the third in the Blessed. And this image, in so far as it belongs to the intellectual nature, exists in the woman as much as in the man; hence Scripture speaks of them in the plural; nevertheless in other respects it is found more in the man because he is the principle.
The image of God in man is according to the Divine Nature and the Trinity of Persons, inasmuch as in God Three Persons exist in One Nature; but great is the difference between this Trinity and the trinity which is found in us; of which Augustine says: "The latter we see rather than believe, while of the former we believe what we do not see."
Moreover, this image exists in the mind according to the twofold procession of intellect and love; in other parts it is only found by mode of vestige, which does not express the likeness of a species to its cause. For in the rational creature the Divine likeness is found in that in which it chiefly excels, namely, in the mind, and is to be understood first as represented by the act of the word and of love; and secondarily, as a consequence as it exists in the habit and faculties of the mind. For the image is that in which the mind approaches to the nature of the Blessed Trinity, viz. in the procession of the word from the speaker, and in love as the bond of connection; and so it exists chiefly in the act; but inasmuch as faculties and habits are the principle of acts, it follows that the Divine image is to be understood also of the soul according to these faculties and habits, because in them the acts exist virtually.
- text taken from Compendium of the Summa Theologica of Saint Thomas Aquinas, by Bishop Berardus Bongiovanni