The image of God in Adam was that he was spiritually good. This is the identification of the image of God in the Belgic Confession of Faith, Article 14; “good, righteous, and holy, capable in all things to will agreeably to the will of God.” That the Confession conceives the image as Adam’s spiritual goodness is evident also in its description of the loss of the image: “being thus become wicked, perverse, and corrupt in all his ways.” This confessional identification of the image and likeness as Adam’s original spiritual goodness is based on scripture’s description of the restoration of the image as the bestowal upon the elect of “knowledge,” “righteousness,” and “holiness” (Ephesians 4:24; Colossians 3:10).
To bear, or be, this image, man had to have a mind and a will with which he could consciously and deliberately be related to God, the divine original that he imaged. Adam had to be human. But the image was Adam’s spiritual goodness. This goodness was the goodness of nature, goodness of what he was in body and soul. His goodness was not merely in deeds, nor in the decisions of his will. Accordingly, loss of the image was corruption of “his whole nature.” The misery of fallen Adam, accordingly, was not only that now he thinks wicked thoughts, wills evil desires, and performs sinful deeds. But “being thus become wicked, perverse, and corrupt in all his ways, he hath lost all his excellent gifts which he had received from God.” according to the Confession.
Identification of the image in which Adam was created as something other than his spiritual goodness of nature is serious doctrinal error. It underestimates the gravity of the fall: the loss of the spiritual likeness to God. Invariably, error concerning the image entails the notion that fallen man retained the image, or at least part of the image. This, in turn, involves the false doctrine that fallen man is still somewhat pleasing to God and even that he can contribute to his salvation, usually by means of a free will that he is thought to have retained. Retention of even a small portion of the image implies that fallen, unsaved man is still somewhat pleasing to God and capable of some good. Thus fallen man escapes the devastating judgment of the gospel upon him: dead in sin, incapable of any good.
From “The Belgic Confession: A Commentary, by Prof D Engelsma.