Sexual misconduct figures prominently in the history of the papacy (another chapter is entitled “Nicholas I and the Pornocracy”) but is hardly the only blot on the institution. Clement VII, the disastrous second Medici pope, oversaw “the worst sack of Rome since the barbarian invasions, the establishment in Germany of Protestantism as a separate religion and the definitive breakaway of the English church over Henry VIII’s divorce.” Paul IV “opened the most savage campaign in papal history against the Jews,” forcing them into ghettos and destroying synagogues. Gregory XIII spent the papacy into penury. Urban VIII imprisoned Galileo and banned all his works.

Most of the popes, being human, were complicated; the rogues had redeeming features, the capable leaders had defects. Innocent III was the greatest of the medieval popes, a man of galvanizing self-­confidence who consolidated the Papal States. But he also initiated the Fourth Crusade, which led to the wild sacking of Constantinople, “the most unspeakable of the many outrages in the whole hideous history of the Crusades.” Sixtus IV sold indulgences and church offices “on a scale previously unparalleled,” made an 8-year-old boy the archbishop of Lisbon and began the horrors of the Spanish Inquisition. But he also commissioned the Sistine Chapel.

Even the Borgia pope Alexander VI, who by the time he bribed his way into office had fathered eight children by at least three women, is credited with keeping the imperiled papacy alive by capable administration and astute diplomacy, “however questionable his means of doing so.”

By the time we reach the 20th century, about 420 pages in, our expectations are not high. We get a disheartening chapter on Pius XI and Pius XII, whose fear of Communism (along with the church’s long streak of anti-Semitism) made them compliant enablers of Mussolini, Hitler and Franco. Pius XI, in Norwich’s view, redeemed himself by his belated but unflinching hostility to the Fascists and Nazis. But his indictment of Pius XII — who resisted every entreaty to speak out against mass murder, even as the trucks were transporting the Jews of Rome to Auschwitz — is compact, evenhanded and devastating. “It is painful to have to record,” Norwich concludes, “that, on the orders of his successor, the process of his canonization has already begun. Suffice it to say here that the current fashion for canonizing all popes on principle will, if continued, make a mockery of sainthood.”

Norwich devotes exactly one chapter to the popes of my lifetime — from the avuncular modernizer John XXIII, whom he plainly loves, to the austere Benedict, off to a “shaky start.” He credits the popular Polish pope, John Paul II — another candidate for sainthood — for his global diplomacy but faults his retrograde views on matters of sex and gender. Norwich’s conclusion may remind readers that he introduced himself as a Protestant agnostic, because whatever his views on God, his views on the papacy are clearly pro-­reformation. “It is now well over half a century since progressive Catholics have longed to see their church bring itself into the modern age,” he writes. “With the accession of every succeeding pontiff they have raised their hopes that some progress might be made on the leading issues of the day — on homosexuality, on contraception, on the ordination of women priests. And each time they have been disappointed.”