How was the image affected by the fall of man?

"Clark believes that the Scriptural doctrine of the imago dei entails in part that man possesses a capacity for knowledge and rationality. 'The scripture teaches that God created man in his own image. From Colossians 3:10 it may be inferred that this image consisted chiefly in knowledge rationality, or logic.'
But what effect has the fall of man had on man's reasoning powers? how did the fall affect the cognitive functions of the imago dei? Clark answers,

The fall seriously damaged God's image in man in all its parts. The intellect became depraved as well as the will. This is the doctrine of total depravity: No part or function of man is free from the effect of sin. However, the different functions are differently affected. While no act of will can be moral in the unregenerate man, it does not follow that no intellectual argument can be valid. . . . Therefore, in order not to assert that the image of God has been completely annihilated, stress must be laid on its component of logic and reason."

- Ronald Nash, Gordon Clark's Theory of Knowledge