I applied my mind to study and to explore by wisdom all that is done under the heavens. What a heavy burden God has laid on the human race!
NIV
And I applied myself by heart and mind to seek and search out by [human] wisdom all human activity under heaven. It is a miserable business which God has given to the sons of man with which to busy themselves.
AMP
And I gave my heart to seek and search out by wisdom concerning all things that are done under heaven: this sore travail hath God given to the sons of man to be exercised therewith.
KJV
Then I applied myself to the understanding of wisdom, and also of madness and folly, but I learned that this, too, is a chasing after the wind.
NIV
And I gave my mind to know [practical] wisdom and to discern [the character of] madness and folly [in which men seem to find satisfaction]; I perceived that this also is a searching after wind and a feeding on it. [I Thess. 5:21.]AMP
And I gave my heart to know wisdom, and to know madness and folly: I perceived that this also is vexation of spirit.
KJV
I said to myself, "Look, I have grown and increased in wisdom more than anyone who has ruled over Jerusalem before me; I have experienced much of wisdom and knowledge."
NIV
I entered into counsel with my own mind, saying, Behold, I have acquired great [human] wisdom, yes, more than all who have been over Jerusalem before me; and my mind has had great experience of [moral] wisdom and [scientific] knowledge.
AMP
I communed with mine own heart, saying, Lo, I am come to great estate, and have gotten more wisdom than all they that have been before me in Jerusalem: yea, my heart had great experience of wisdom and knowledge.
KJV