With the publication of his 95 Theses, Martin Luther articulated a critique of the Church and the institution of the Pope, which would soon have an unprecedented impact. The theses sparked a debate during which Luther was excommunicated, ultimately leading to the separation of the Evangelical-Lutheran Church from the previously dominant Roman Catholic Church in the following decades. Even before the powerful church reformer Martin Luther, there were theologians like John Wycliffe in England and Jan Hus in Bohemia who challenged the foundations of the existing Church with their critiques and called for extensive reforms. In both cases, the discussion did not remain limited to theological questions; social-revolutionary movements also emerged. The book traces the life paths and main strands of thought.