Was ist Aufklarung? What is Enlightenment? The German periodical, Berlinische Monatschrift, posed the question, and in November 1784 published a response penned by no less an authority than the philosopher Immanuel Kant. For his answer Kant drew on a phrase attributed to the 1st century B.C. Roman poet Horace: Sapere Aude.

Enlightenment is man's release from his self-incurred tutelage. Tutelage is man's inability to make use of his understanding without direction from another. Self-incurred is this tutelage when its cause lies not in lack of reason but in lack of resolution and courage to use it without direction from another. Sapere aude! "Have courage to use your own reason!" -- that is the motto of enlightenment.

Immanuel Kant, "What is Enlightenment?" (1784).