By Walter J. Daly
Transactions of the American Clinical and Climatological Association, Vol.109 (1998)
Introduction: The Middle Ages should be known as a period of intellectual activity rather than historical glamour. It was also a period of hardship, pestilence, and violence. But it was the period of true giants such as Thomas Aquinas, who systematized religious theory. Like Anselm and Hugh of St. Victor, he even developed logical proofs for the existence of God. It was the period of Albertus Magnus (St. Albert the Great), who worked to reconcile much of Aristotle with Christian theology. Like Aristotle, he linked philosophy and science. It was also the period of the ruler, Frederick II, who flaunted convention, was excommunicated several times, but was reputed to foster intellectuals and the medical school at Salerno. And it was the period of Innocent III, perhaps the greatest leader of them all.
During this time of intellectual activity and controversy, Peter of Spain lived out a long and fruitful life as a scholar known for his works on logic, as a scholar-physician who wrote widely and was sought by his contemporaries as their doctor, and as a churchman so successful that he became Pope, John XXI. He even made it into Dante’s Paradise, where he had a place among the scholars. Peter was not the most outstanding in any single field, though he was one of the most important medieval physicians; he was the only man of his time with his breadth of achievement. It is known that John XXI died in 1277. His date of birth remains unknown, perhaps as early as 1205 or as late as 1220.
Peter was probably born in Lisbon and educated there in the Cathedral School until he was sent to Paris for a university education. If he was born as early as 1205, he may have been in Paris by the early 1220’s. There he studied the arts, philosophy, theology and perhaps medicine. Some have argued that he also attended the medical school in Montpelier or Salerno; indirect evidence suggests a Salernitan connection; perhaps he just visited. After leaving Paris, he traveled through southern France, Spain and Italy. It was probably in Spain that he wrote and “published” his most famous book, the Tractatus, or Summulae Logicales. Early on, in this long treatise, he reasoned that logic is “the art of arts and the science of science, the preparation for all other sciences”. This work was the standard text of logic for the next several hundred years.
In 1245, he was in Siena as a Professor of Medicine. Subsequently, he had Church assignments in Spain and Portugal. In 1272, he became physician to Pope Gregory X. By 1273, he was a Cardinal and, in 1276 he was elected Pope.