The past week we learned the נהנה's last speech before he leaves Kohelet. Both the עמל and the כחם think that effort or wisdom can help make the world a better place. The נהנה responds to that saying man can't save himself through his actions. He realizes that no matter what you do everyone has the same fate- death. The sinners and righteous have the same fate, the good and the bad have the same fate, the pure and impure have the same fate, so what is the point? Once you are dead you are forgotten and lost. Nothing will happen once you die so you might as well eat, drink, and party. The נהנה has some truth to his words. We don't know what will come after this world, if anything at all.