The Age of Enlightenment valorized human reason, and Kant is squarely situated in this tradition. The capacity for independent thought is among the most important components of his definition of enlightenment, which he says from the outset entails developing from immaturity into full adulthood. Enlightenment for Kant, like other Enlightenment philosophers, means overcoming persistent sources of error by returning to a source of true knowledge. For Kant this source is the capacity to reason.

The sources of error Kant is concerned with include custom and tradition, but they also include individuals’ own prejudices, biases, and interests. All humans possess reason; it is a public resource, so it does not favor any one person’s point of view over anyone else’s. Kant tells readers to “Have the courage to use [their] own understanding” (41, 8:35), but the structure of everyone’s understanding is the same, as his other works, especially the Critique of Pure Reason, make clear.

Thinking for oneself, then, means thinking disinterestedly—i.e., from a broader point of view than just one’s own. In a sense, thinking for oneself from the standpoint of reason means thinking for everyone. This is why Kant puts so much emphasis on the public use of reason over the private.