This whimsical, apparently obvious and typically teasing quote from Knox (see post below) reflects his understanding of the image of God. Calvin's got a similar take on it at the beginning of the Institutes:
Our wisdom, in so far as it ought to be deemed true and solid Wisdom, consists almost entirely of two parts: the knowledge of God and of ourselves. But as these are connected together by many ties, it is not easy to determine which of the two precedes and gives birth to the other. For, in the first place, no man can survey himself without forthwith turning his thoughts towards the God in whom he lives and moves; because it is perfectly obvious, that the endowments which we possess cannot possibly be from ourselves; nay, that our very being is nothing else than subsistence in God alone. In the second place, those blessings which unceasingly distil to us from heaven, are like streams conducting us to the fountain.
-Calvin, John. Institutes of the Christian Religion I.1.1
Oh, and this from the next paragraph:
On the other hand, it is evident that man never attains to a true self-knowledge until he have previously contemplated the face of God, and come down after such contemplation to look into himself.
Calvin had been reading his DBK.