Herman Boerhaave, who held professorships in medicine, botany, and chemistry at the University of Leiden, is often considered the most important medical teacher after Galen. Known during his lifetime as "The Teacher of Europe," his reputation was purported to have reached all the way to China. Previously, historians of science and medicine have stressed the mechanical aspects of his teachings, but have neglected the principles behind them, many of which are alien to modern science. This book shows that Boerhaave's natural philosophy and methodology were rooted in his deep religious faith, and that Calvinism guided much of his scientific thought.