A History of Free Thought surveys three millennia of challenges to inherited and enforced belief, while resisting the assumption that freethought is simply equivalent to atheism, secularism, science, or inevitable intellectual progress. Beginning with ancient Asian, Near Eastern, Greek, and Roman traditions, the course examines how religious contact, naturalistic explanation, skepticism, and philosophical inquiry opened alternatives to orthodoxy. It follows heterodox currents through early Christianity, Islam, medieval Christendom, the Renaissance, and the Reformation, attending to allegory, reason, toleration, persecution, and institutional authority. The course then traces deism, biblical criticism, rationalism, materialism, and Enlightenment thought across Europe and America. Its nineteenth- and twentieth-century lessons connect popular radicalism, scientific naturalism, social theory, literature, church–state separation, and civil liberties. The concluding comparison with Soviet scientific atheism reframes free thought as independent judgment opposed to monopolies over belief, including officially atheistic ones.