Pope Pius IX promulgated the encyclical Quanta cura on December 8, 1864, in the Vatican, embodying the Catholic Church's stance in a rapidly changing social and political landscape marked by liberalism and secularism. This encyclical was accompanied by the Syllabus of Errors, a document that enumerated eighty specific propositions that were denounced as contrary to Catholic doctrine. These propositions included critiques of modern rationalism, socialism, and the advocacy for the separation of church and state, reflecting a concern over the rising secular ideologies that threatened traditional Catholic teachings.

The issuance of Quanta cura and the Syllabus of Errors came at a time when Europe was experiencing significant political upheaval, characterized by revolutions, the unification of Italy, and a growing push towards national identities over religious affiliations. The Pope positioned himself and the Church as defenders of the institution against perceived threats posed by modernist thought. By explicitly condemning these liberal ideas, Pius IX sought to galvanize the faithful and reassert the authority of the papacy in both spiritual and temporal matters.

The encyclical and Syllabus gained a mixed reception among European Catholics, with some viewing it as a necessary defense of faith, while others saw it as an outdated response that did not engage with contemporary issues. The encyclical laid a foundation for future papal teachings and marked one of the last strong resistances to modernity within the Church, as it set the stage for further theological and political disputes that unfolded in subsequent decades.