Read Ecc. 1:12-18
Solomon says that all pursuits 'under the sun' will bring no lasting fulfillment to the person who accomplishes that pursuit. There are people who hear this and want to say to Solomon… “Maybe for you but my life will be better.” Verses 12-18 is Solomon’s response to those people. He laughs at them as he points out the fact that he's the “king over all Israel.” At the time that Solomon writes Ecclesiastes there has been about forty years of peace and he's been able to do whatever he wanted with Israel’s wealth yet it was all simply a puff of smoke. No person will find eternal purpose in an earthly pursuit no matter how great they are.