Peter of Spain was born in Lisbon, Portugal, probably around 1205, or a bit earlier. It is likely that his father, Rebolo Julianus, was a nobleman and a man of some wealth. Peter studied the arts at the University of Paris "for many years," by his own report, presumably for a longer time than required by the curriculum. He was probably at Paris from about the age of fifteen, when one usually began attendance at the university in those days. It has been pointed out that he promised himself a long pontificate when elected pope in 1277, which might seem to count against such an early birth; but the basis of this expectation was his medical skill, not his youth.

Generally six years were required to finish the arts curriculum, so he would have taken up theology in 1226 if he were on schedule; but it seems possible that he was...