text: During the reign of this pope, Marcantonio Pacelli began publishing The Roman Observer, which reports on the daily activities of the Holy See.
full_question: During the reign of this pope, Marcantonio Pacelli began publishing The Roman Observer, which reports on the daily activities of the Holy See. This man adopted a six-year-old Jewish boy named Edgardo Mortara on the grounds that a Jewish family should not be allowed to care for a baptized child. This pope issued the encyclical Quanta Cura at the same time as he released a document condemning eighty propositions, the Syllabus of Errors. This pope issued the dogma of the Immaculate Conception at the First Vatican Council, which he convened. For 10 points, name this longest-reigning pope in history who decreed the dogma of papal infallibility.
first_sentence: During the reign of this pope, Marcantonio Pacelli began publishing The Roman Observer, which reports on the daily activities of the Holy See.
raw_answer: Pius IX [or Giovanni Maria Mastai-Ferretti; prompt on Pius]