Who he was
Peter, son of Julian, studied at Lisbon and at the University of Paris, where he heard Albert the Great, and became a professor of medicine at Siena. He served as physician to Gregory X, was chosen Archbishop of Braga and was made Cardinal-Bishop of Tusculum. He was elected at Viterbo in September 1276 and crowned on 20 September; there was in fact no John XX, so his number skips one. As pope he worked for peace between France and Castile and pressed the union with the Greek Church, but on 14 May 1277 the ceiling of a study he had added to the palace at Viterbo fell on him, and he died six days later.
What he is remembered for
He is the only Portuguese pope and one of the few scientists to hold the office. His textbook on logic, the Summulae logicales, was used in universities for almost three hundred years, and he also wrote on medicine and diseases of the eye.
Sources
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