Sapere aude is the Latin phrase meaning "Dare to know"; and also is loosely translated as "Dare to know things", or even more loosely as "Dare to be wise" Originally used in the "First Book of Letters" (20 BC), by the Roman poet Horace, the phrase "Sapere aude" became associated with the Age of Enlightenment, during the 17th and 18th centuries, after Immanuel Kant used it in the essay, "Answering the Question: What Is Enlightenment?" (1784). As a philosopher, Kant claimed the phrase "Sapere aude" as the motto for the entire period of the Enlightenment, and used it to develop his theories of the application of reason in the public sphere of human affairs.