This is an evil among all things that are done under the sun, that there is one event unto all: yea, also the heart of the sons of men is full of evil, and madness is in their heart while they live, and after that they go to the dead.
This is an evil among all things ... Not only "there is one event unto all," but "also the heart of the sons of men" makes this fact a reason for 'madly' persisting in evil "while they live, and after that (they go) to the dead." Sin is "madness."
Madness (is) in their heart - mad thoughts about God's government, because of the adversity of the godly, tempt them to take wrong courses to help. themselves (Malachi 3:13-14).
The dead - (Proverbs 2:18; Proverbs 9:18.)