Pope Pius IX's Syllabus of Errors

Against the backdrop of the 1848 revolutions, the Italian Risorgimento, and the loss of the Papal States, Pope Pius IX issued the encyclical Quanta Cura in 1864. Attached to it was a list of eighty "errors of our time" – the Syllabus.

Among the condemned errors were the separation of church and state, secular education, and freedom of religion. Also condemned were the notion that Protestantism is a form of Christianity and the idea that the pope could or should reconcile himself with progress, liberalism, and modern civilization.

The document provoked widespread protest from both Catholics (especially in France and Britain) and Protestants. In the US it confirmed suspicions about Catholic loyalty.