On a summer evening in 1505, a young German student was walking along a path through the countryside. A violent thunderstorm raged. Suddenly, lightning struck very close to the young man, knocking him to his death. The student, fearing for his life and the salvation of his soul, made a vow. That young man's name was Martin Luther, and that lightning bolt would change the course of his life and that of Christianity as a whole.

Martin Luther was born in the German region of Thuringia in 1483, into an emerging middle-class family. He grew up immersed in a religiosity steeped in magic and superstition. Spirits, witches, and demons, in constant conflict with armies of saints, populated the German religious imagination of the time. Throughout, the image of an omnipotent God, distant from man, was dominant, perceived as a stern judge, accustomed to condemning men to hell for their sins. All of this would later influence the development of his thought.

In 1501, at his father's behest, young Martin began studying law at the University of Erfurt. Although he did not go down in history as a jurist, this period was nonetheless important. Indeed, it was while he was studying in Erfurt that he first had the opportunity to read the Bible. In the Catholic world of the time, it was rare for laypeople to have access to sacred texts. He later said he "enjoyed reading" it and hoped to be fortunate enough to own that book one day. He did not know it then, but thanks to him, a few years later, that book would become widely distributed.

However, the event that changed his life occurred in 1505. During his journey between the town of Mansfeld and the village of Stotterheim, he was caught in a violent thunderstorm. His fear was not only that of dying, but of going to hell. He was not a particularly hardened sinner, but it had been some time since he had confessed or received the sacraments, which were then considered essential for salvation. He therefore appealed to Saint Anne, whose cult was pervasive in Germany, promising to become a monk if he survived. It is amusing to note that, a few years later, his religious reform would abolish both the cult of saints (including that of Saint Anne) and religious orders (including friars). Luther kept his vow, joining the Augustinian order, where he developed the ideas that gave rise to the Protestant Reformation. The history of Christian Europe would never be the same again.