According to Immanuel Kant, enlightenment is when a person grows out of his self-imposed immaturity. He defines immaturity as one's inability to use his own understanding without the guidance of another. He says that people impose immaturity on themselves because they fear the use of their own understanding without someone else's help. Furthermore he adds that laziness and cowardice cause people to gladly remain immature for life. Because of these qualities, he says that others may easily establish themselves as the guardians or authorities on certain subjects. He gives the following examples of guardians, "a book to serve as my understanding, a pastor to serve as my conscience, a physician to determine my diet for me, and so on." He says that guardians will often warn you of dangers you could encounter should you attempt not to use their aid. They tell the people whom they guard that the step to maturity is very dangerous and difficult. He says that this frightens people from making attempts towards maturity.

Kant states that it is often difficult for people to emerge from immaturity. He says that people would often remain content in a state of immaturity. According to him, rules and formulas bind people to a state of immaturity. A person, he says, who would dare to defy the rules and formulas would only be taking a small step towards maturity because he is unaccustomed to this kind of free movement. Only a few people, according to Kant, have succeeded in emerging from immaturity. He says that such people have done so by cultivating their minds.

Kant says that the only thing required for enlightenment is freedom, namely the freedom to publicly use reason. By public use of reason he means, a scholar's use of reason before the entire literate world. He says that this public use of reason alone can bring about enlightenment among people. Private reason, he points out, may be narrowly restricted as long as it does not hinder the enlightening process.

Thus, freedom is essential for enlightenment. People must be able to express their thoughts. By spreading ideas and information, people will be able to be their own guardians because they will have all the things necessary to do so. By allowing freedom of thought, people will spread ideas which will urge others to think for themselves.