The philosopher Immanuel Kant published “What Is Enlightenment?” (full title, “An Answer to the Question: What Is Enlightenment?”) in 1784. This guide uses the translation by Ted Humphrey from the volume Perpetual Peace and Other Essays, published by Hackett in 1983. All quotations will be cited with the page number from this volume followed by the page number from the official Akademie collection of Kant’s works. Most publishers will put the latter in the margins of the text for ease of reference for readers using different editions. (The essay appears in volume eight of the collected works, so each marginal citation will be formatted “8:marginal #.”)

Kant submitted his essay, which is now recognized as one of the key texts of the Enlightenment, to the Berlinische Monatsschrift (Berlin Monthly) in response to an open invitation to reply to the question, “What is enlightenment?” Kant gives his answer from the outset: “Enlightenment is man’s emergence from his self-imposed immaturity” (41, 8:35). (Kant defaults to masculine terms like “man” and “mankind” as well as masculine pronouns throughout, both because of convention and because of the gender bias of his time; this guide updates the language to reflect greater gender neutrality.) Kant suggests that the unenlightened have not developed the ability of Thinking for Oneself or making decisions based on one’s own reason. In this, they are much like children who have not yet developed the full capacity to reason. This state is self-imposed, however, because it is the result of “laziness and cowardice” rather than lack of capacity (41, 8:35). Enlightenment’s “motto,” then, is “Sapere Aude! ‘Have courage to use your own understanding!’” (41, 8:35).

Kant observes that when people gladly remain unenlightened, their thinking and their beliefs—and hence their decisions—are easily controlled by others, who install themselves as their “guardians” or external authorities. Because these authorities encourage people to remain unenlightened, it is difficult for an individual to achieve enlightenment. Enlightenment is more likely at the collective level—i.e., for the public. Kant says that the only prerequisite for the enlightenment of the public is the freedom to make public use of one’s reason.

Kant distinguishes public uses of reason from private uses. The public use of reason, he says, is “the use that anyone as a scholar makes of reason before the entire literate world” (42, 8:37). In other words, people reason publicly when they put forth positions and provide arguments for them in the public sphere—what Kant elsewhere calls Freedom of the Pen. Private uses of reason, on the other hand, are those that people employ in more specific contexts, such as their jobs. To illustrate this, Kant employs the examples of a member of the military, a tax-paying citizen, and a clergyman throughout the essay. He acknowledges that private uses of reason can be subject to all sorts of restrictions, while public uses of reason must be unrestricted for the public to achieve enlightenment. For instance, the military officer must obey the orders of his superiors without question; however, the same officer, acting as a scholar rather than as a member of the military, must also be able to publicly criticize the orders and the strategies of those above him in the military hierarchy (e.g., by writing an editorial in a newspaper).

Kant devotes the most attention to the example of the clergyman because he sees enlightenment in the arena of religion and spiritual well-being as the most important. The latter half of the essay, then, turns to an argument against any government interference in free speech or free thinking on religious matters. Kant says that it is never legitimate to restrict public discussion or criticism of religious beliefs and practices, advocating a form of The Separation of Church and State. Even those in the clergy, who must follow the dictates of their church when acting as clerics, must be able to publicly criticize those same dictates.

Kant states that while the public has some progress to make before it can be considered enlightened, he and his contemporaries nevertheless “live in an age of enlightenment” (44, 8:40). Rulers who recognizes the importance of free discussion of religious matters make this possible, and Kant praises Prussia’s King Frederick the Great for being the first monarch to allow for completely free discussion of religious and spiritual issues. Thus, Kant says, the time of his writing “is the age of enlightenment, the century of Frederick” (45, 8:40).

Kant closes on a confident and hopeful note: The free public use of reason under Frederick the Great is sure to bring about the public’s enlightenment, even though other freedoms may be strictly curtailed. History has put in place the conditions for humanity to begin thinking for itself, which will inevitably improve government institutions and bring about a more just republic.