As he often does, Nietzsche omits a premise required by his syllogism, leaving to the reader the task of filling it in.
Let C = admitting a belief because it is a custom, let DCL = being dishonest, cowardly, and lazy, and let M = morality. Nietzsche’s observation takes this form:
If C, then DCL.
If DCL, then M.
Obviously, we’re missing a premise:
If M, then C.
By morality, Nietzsche seems to have in mind beliefs, values, and practices that are adhered to merely because it’s customary to do so. This is contrary to the leading principle of the Enlightenment, according to which something should be done only if it is rational to do it.
Kant expressed this view in “What is Enlightenment?” (1784) Those who don’t base their actions on reason are lazy, cowardly, and childish, he said. We should be moral because we see that it’s rational to do so, not out of mere habit.
Nietzsche, however, denies the existence of moral motivation as Kant conceives it. No one obeys a moral principle merely because no other course of action can be rationally justified. If there is morality at all, it’s because morality serves the purposes of the group and the group has managed to institutionalize and perpetuate it.
If that’s not good enough for Kant, Nietzsche is suggesting, he has a problem: he must choose between reason and morality. To insist on reason is to reject morality, and to embrace morality is to betray reason.
Below, moral instruction.