This encyclical letter of Pope Pius IX was promulgated in 1864 and issued with the attached Syllabus of Errors. The document was dispatched to all the bishops of the Catholic world "in order that these same bishops may have before their eyes all the errors and pernicious doctrines which he has reprobated and condemned." The Syllabus is a catalogue of eighty propositions, which the pope condemned as erroneous, and which are considered to form the basis of the heresy of Modernism, which has been anathematized by a number of succeeding pontiffs.
