New light appeared on Spain’s intellectual horizons in the 1680s, and for more than a century afterwards the impulse for renewal through skeptical questioning of past truths and methods brought significant changes in cultural attitudes and practices. Yet the context of Spain’s intellectual and social life was distinctive, and just as the French experience of Enlightenment was different from Britain’s, so Enlightenment in Spain must be examined on its own terms, though from a reasoned comparative perspective. For the intellectual historian, Enlightenment primarily concerns knowledge and the move from authoritative, privileged forms of truth to a skeptical, reasoning, empirically based conception. John Locke’s assertion in 1690 of the sense-data basis of knowledge and the role of the human understanding in processing experience gave new significance to the individual and the action of the mind in subscribing to and appropriating truths. An assumption by the individual of responsibility for challenging error or unquestioned authority effected a process of personal emancipation and self-confidence. Locke’s theory de-emphasized the reliance on authority, especially religious, and, in combination with Francis Bacon’s empirical paradigm of scientific research, this led to the secularized concept of knowledge familiar today. The assault on authoritative knowledge challenged the power of those asserting it, and in Spain the existence of an Inquisition, whose vigilance over theological orthodoxy embraced the sciences and philosophy, implied a lack of freedom and consequent danger when arguing for change. Daring to know, in Immanuel Kant’s opportune allusion to Horace (Sapere aude), entailed risk in Spain. The Catholic Church asserted a monopoly on knowledge and truth, punishing the written and oral expression of intellectual dissidence.