Next year marks the fifth centenary of one of the few precisely datable historical events that can be said to have changed the world forever. In 1517, an unknown German professor from an undistinguished new university protested against the sordid trade in religious benefits known as “indulgences,” which were then being peddled around Germany to fund grandiose plans to rebuild St. Peter’s Basilica in Rome. Martin Luther’s protest initially took the form of a public challenge to an academic debate on a swathe of theological niceties. But this was the first age of print, and Luther was a publicist of genius. His list of topics for debate, in the form of Ninety-Five Theses, was printed as a broadsheet (though the legend that he nailed them to a church door is, sadly, probably untrue). The theses nonetheless became the world’s most improbable bestseller. What might have been a technical academic exercise in a Wittenberg lecture hall rapidly escalated into a fundamental questioning of the theological underpinning of Western Christianity. In its wake, Europe divided, roughly north and south, and the peoples of Europe were pitched into a series of murderous ideological wars in which tens of thousands died, and during which the religious, cultural, and political map of Europe was redrawn. We are all still living with the consequences.