Book excerpt: Ockham Explained is an important and much-needed resource on William of Ockham, one of the most important philosophers of the Middle Ages. His eventful and controversial life was marked by sharp career moves and academic and ecclesiastical battles. At 28, Ockham was a conservative English theologian focused obsessively on the nature of language, but by 40, he had transformed into a fugitive friar, accused of heresy, and finally protected by the German emperor as he composed incendiary treatises calling for strong limits on papal authority. This book provides a thorough grounding in Ockham's life and his many contributions to philosophy. It begins with an overview of the philosopher's youth and the Aristotelian philosophy he studied as a boy. Subsequent chapters cover his ideas on language and logic; his metaphysics and vaunted "razor," as well as his opponents' "anti-razor" theories; his invention of the church-state separation; and much more. The concluding chapter sums up Ockham's compelling philosophical personality and explains his modern appeal.