From Immanuel Kant’s An Answer to the Question: ‘What is Enlightenment?’:
Enlightenment is man’s emergence from his self-incurred immaturity. Immaturity is the inability to use own’s own understanding without the guidance of another. This immaturity is self-incurred if its cause is not lack of understanding, but lack of resolution and courage to use it without the guidance of another. The motto of enlightenment is therefore: Sapere aude! Have courage to use your own understanding!
Laziness and cowardice are the reasons why such a large proportion of men, even when nature has long emancipated them from alien guidance (naturraliter maiorennes), nevertheless gladly remain immature for life. For the same reasons, it is all too easy for others to set themselves up as their guardians. It is so convenient to be immature!