With Persian Letters (1721) Montesquieu opens the Enlightenment era. In this fiction, more similar to the essay than to the novel but good-humored and ironic, the France as seen by Persian visitors satirizes the practices of an ossified society and desacralizes established values, in particular those related to religion and authority. Its key word is diversity: Ethics and metaphysics alternate with derision to affirm notions as fundamental as the primacy of reason or the unalienable right to happiness and freedom for all. For such daring touches the book was banned in France, but its success was as meteoric as it was durable and extended to all of Europe. A posthumous edition in 1758, enriched and corrected, shows that Montesquieu maintained his boldest positions as well as justifying his approach. A genuinely critical kind of thought was born that combined philosophy and fiction, amusement with reflection, and forthwith defined the field of Enlightenment.