Kant first defines enlightenment (Aufklärung in German) in a negative manner, as a state of no longer being immature. The positive definition, then, is that enlightenment is a state of full human development in which people decide what to do and what to believe based on reason rather than outside authority; it is a form of Thinking for Oneself. Kant’s main concern in “What Is Enlightenment?” is with the enlightened public rather than with individuals, so enlightenment here is the public’s capacity to think for itself and to self-govern.

Kant’s conception of freedom is much narrower than the contemporary understanding of freedom as the absence of constraints on one’s actions. Simply being able to do whatever one wants would actually not be freedom from Kant’s perspective, as it would involve being a servant to one’s inclinations, desires, and impulses rather than being one’s own master. For Kant, freedom is autonomy in the sense that derives from the word’s Greek origins: giving the law to oneself. Furthermore, while Kant argues for free thought and expression in “What Is Enlightenment?”—i.e., Freedom of the Pen—he accepts many restrictions on the freedom of private citizens.