Kant’s problem is not so much with his ambition but with his unwillingness to admit failure. Mathematicians have successfully resolved countless mathematical controversies with proofs, but not one moral controversy has ever been resolved with a proof from first principles. Kant wants so badly to prove that his moral opinions are correct that he’s blind to the flaws in his arguments. In other words, Kant crosses the line from reasoning to rationalization, and that’s why Nietzsche is chuckling.
