Albert Barnes Commentary Ecclesiastes 1:18

"For in much wisdom is much grief; and he that increaseth knowledge increaseth sorrow." — Ecclesiastes 1:18 (ASV)

We become more aware of our ignorance and powerlessness, and therefore sorrowful, as we discover more of the order of nature and the plan of Providence in the government of the world; every discovery serves to convince us that more remains concealed of which we had no suspicion before.