Albert Barnes Commentary Job 27:12

"Behold, all ye yourselves have seen it; Why then are ye become altogether vain?" — Job 27:12 (ASV)

Behold, all of you yourselves have seen it – You have had an opportunity to trace the proofs of the wisdom of God in his works.

Why then are you so altogether mistaken? – Why is it that you maintain such opinions – that you show no more knowledge of his government and plans – that you argue so inconclusively about him and his administration! Why, since you have had an opportunity to observe the course of events, do you maintain that suffering is necessarily a proof of guilt, and that God deals with all people in this life according to their character?

A close observation of the course of events would have taught you otherwise. Job proceeds to state what he believes to be the exact truth on the subject, and particularly aims, in the following chapter, to show that the ways of God are inscrutable, and that we cannot be expected to comprehend them and are not competent to pronounce upon them.