Tom Holland, the British historian and writer, argues that Western civilization's most fundamental values, including those claimed by secular movements, are rooted in Christianity's revolutionary transformation of the ancient world. Holland traces how Christian ideas about the dignity of every human being, the priority of the weak over the strong, and the separation of religious and political authority reshaped societies that had operated on very different principles. He shows how concepts that seem self-evidently true to modern Westerners, including human rights, the moral equality of persons, and skepticism of power, emerged from Christian teaching and practice rather than Greek philosophy or Enlightenment reason. The book ranges from Paul's letters through the Crusades, the Reformation, and the French Revolution to contemporary debates about sexuality and secularism, demonstrating Christianity's continuing influence even in movements that define themselves against it. Holland writes as someone who lost his childhood faith and then came to recognize how profoundly Christian categories shaped his own moral sensibilities. The book does not argue for Christianity's truth but for its historical importance in creating the mental furniture of the Western world. Readers will find their assumptions about the secular origins of modern values productively challenged, whether or not they share Holland's conclusion that the West cannot understand itself without understanding its Christian inheritance.