Charles Ellicott Commentary Ecclesiastes 1:17

"And I applied my heart to know wisdom, and to know madness and folly: I perceived that this also was a striving after wind." — Ecclesiastes 1:17 (ASV)

Madness and folly are words we should not expect to find in this context, and accordingly, some interpreters have attempted, based on variant readings, to substitute for them words of the same nature as “wisdom and knowledge,” but see Ecclesiastes 2:12; Ecclesiastes 7:25. Taking the text as it stands, it means to know wisdom and knowledge fully by a study of their contraries. The word for “madness” is peculiar to this book, but the corresponding verb occurs frequently in other books.