Kant’s appeal in “What Is Enlightenment?” is not primarily intellectual but ethical. Enlightenment, Kant says, “is man’s emergence from his self-incurred immaturity.” Immaturity he defines as “the inability to use one’s own understanding without the guidance of another,” and this immaturity is “self-incurred” when the cause is “lack of resolution and courage” to use one’s understanding without guidance from outside authority. “Laziness and cowardice” are the two chief impediments to enlightenment, particularly laziness, since it is so easy to be immature and simply pay for someone to make decisions for us.

Famously, he quotes from Horace. But the “sapere aude” does not mean “be wise” but “dare to be wise,” and Kant’s emphasis is on the daring as much as the wisdom.