Adam Clarke's Commentary on the Bible

Verse 13 (Ecclesiastes 1:13)

And I gave my heart to seek and search - While Solomon was faithful to his God he diligently cultivated his mind. His giving himself to the study of natural history, philosophy, poetry, etc., are sufficient proofs of it. He had not intuitive knowledge from God; but he had a capacity to obtain every kind of knowledge useful to man.

This sore travail - This is the way in which knowledge is to be acquired; and in order to investigate the operations of nature, the most laborious discussions and perplexing experiments must be instituted, and conducted to their proper results. It is God's determination that knowledge shall be acquired in no other way.

- Adam Clarke's Commentary on the Bible