Innocent III (ca. 1160-1216), an Italian aristocrat, theologian, and canon lawyer, reigned as pope from 1198 to 1216. His pontificate has customarily been taken to mark the most splendid moment of the medieval papacy.

Born Lothar of Segni, the future pope was the son of Count Thrasimund of Segni. He studied theology at Paris and law at Bologna, the leading medieval centers of these studies, and at about the age of 30 had already attained the rank of cardinal deacon. He owed his elevation to the Sacred College to his uncle, Pope Clement III, but this could not obscure the fact that he was a man of outstanding ability and energy. Not even the temporary eclipse of his fortunes during the pontificate of Celestine III prevented the cardinals from turning to him in January 1198, when that aged and unsuccessful pontiff died. The years of eclipse, indeed, had enhanced rather than diminished...