The term rationalism, dating from around the middle of the 17th century, is usually understood as the philosophical outlook which stresses the power of reason over faith, emotion or instinct. This text collects together those figures who have championed the cause of rationalism over three centuries, including theists, pantheists, atheists, materialists, agnostics, secularists, monists, and positivists. It contains not only philosophers but teachers of science, political theorists, historians, and artists. Each entry in the book lists the subject's birth and death dates, details of their education and occupation, and evidence of their rationalist views. European, American and minor figures are included.