And thou sayest, How doth God know? Job had not said this in so many words, but, by equalizing the godly and the wicked (Job 9:22; Job 21:23-26), he might be supposed to mean that God took no note of men's conduct, and therefore had not a perfect knowledge of all things.
The psalmist implies that many men so thought (Psalms 10:11; Psalms 73:11; Psalms 94:7). Can he judge through the dark cloud? rather, through the thick darkness. God was supposed to dwell remote from man, in the highest heaven, and, according to many, "clouds and darkness were round about him" (Psalms 97:2)—he "dwelt in the thick darkness" (1 Kings 8:12)—he "made darkness his secret place; his pavilion round about him was waters, and thick clouds of the skies" (Psalms 18:11).
The imagery was, no doubt, at first used in reference to man's inability to see and know God; but when men became familiar with it, they turned the metaphor round, and questioned God's ability to see and know anything about man.
Job had not really ever shared in these doubts; but it suits Eliphaz's purpose to malign and misrepresent him.