'Delusion' in the Bible

So {I dedicated myself} to learn about wisdom and [to] learn about delusion and folly. However, I discovered that this also [is] chasing wind.

Next, I considered wisdom, as well as delusion and folly. What can anyone [do] who will come after the king that has not already been done?

I committed myself to understand, to learn, to search for wisdom and explanations, and to understand both the evil that is foolishness and the stupidity that is delusion.

This [is] the {injustice} that is done under the sun: the same fate [comes] to everyone. Also the hearts of {humans} are full [of] evil; delusion [is] in their hearts during their lives, and then they die.

He begins by saying what is foolish and ends by uttering what is wicked delusion.