According to Immanuel Kant, enlightenment is a person’s ability to analyze and understand events without making use of another person’s guidance; it is a person’s ability to reason. He explains that most people fail to achieve enlightenment because of laziness or/and fear of the unknown, or rather fear of failure. People are slow to develop their own critical analysis skills because there are already many others willing to do this for them—what Kant calls guardians. The guardians include pastors, whose work it is to read and understand the Bible, or whatever spiritual book that is specific to a religion, and then present their findings to the congregation; doctors, who have studied medicine and whose work it is to diagnose illnesses, give prescriptions, and so on. The result is that people are not incentivized to seek personal enlightenment; they would rather pay others, the guardians, to help them out, to think for them.
Kant goes on to discuss freedom as a core component of enlightenment. Towards this end, he identifies two forms of reasoning: the public and the private “use of one’s reason.” He defines “private use of one’s reason” as reasoning employed by an individual in a civic post or formal position of appointment or employment, such as a civil servant, police officer, church minister, or senator. He notes that an individual’s reasoning in such a capacity is restrained by his or her office, hence not free, as he or she will be “carrying out the orders of others.” On the other hand, an individual’s reasoning out of the private domain (public use of reason) should be unrestrained (free) so that, for instance, a pastor in his public use of reason should be free to “publish his criticisms of the weaknesses of the existing institutions.” He notes that many of the hindrances to enlightenment are being done away with as people gain more freedom in their thinking.
In the essay "What is Enlightenment?" (or "Answering the Question: What is Enlightenment?"), Kant says that enlightenment is "man's emergence from his self-imposed nonage." This means that enlightenment is a man/woman progressing from a state of self-imposed naivete to a state of autonomous reason. One must have courage to leave behind the naive (nonage - immature or infantile) state to embrace the self-reliant state of an enlightened individual.
An enlightened person has ceased letting others think for him and takes on that responsibility himself. In addition to having courage, one must have the freedom necessary to use reason in all aspects (private and public, individual and social) of one's life. The more free a whole society is, the more enlightened that society can become.
Enlightenment is not a utopian end but an ongoing process. Therefore an enlightened society should continue to endorse the freedom to question current institutions and knowledge in order to continue to progress.
But, while this provisional order continues, each citizen (above all, each pastor acting as a scholar) should be left free to publish his criticisms of the faults of existing institutions.
In an enlightened society, a ruler or authority who is enlightened will recognize the benefits of encouraging free thought; "he knows that there is no danger in permitting his subjects to make public use of their reason and to publish their ideas concerning a better constitution, as well as candid criticism of existing basic laws."