Existentialism according to Ecclesiastes 2:11-12

11. Then I looked on all the worlds that my hands had wrought, and on the labour that I had laboured to do: and, behold, all was vanity and vexation of the spirit, and there was no profit under the sun.

12. And I turned myself to behold wisdom, and madness, and folly: for what can the man do that cometh after the king? even that which hath been already done.