After you send him the $1000, when you spend all day on 4chan, it is no longer stupid because of the $1000 you get back by doing it. Therefore it isn’t an akratic action. Therefore you don’t get the $1000 for it after all. This is a contradiction, and “therefore” it’s impossible for you to do it :-).
Nope, indeed you don’t get it :-).
After you send him the $1000, when you spend all day on 4chan, it is no longer stupid because of the $1000 you get back by doing it. Therefore it isn’t an akratic action. Therefore you don’t get the $1000 for it after all. This is a contradiction, and “therefore” it’s impossible for you to do it :-).
It’s just a philosophical joke.