Denis Diderot was a philosopher and the chief editor of the Encyclopedia, or Reasoned Dictionary of the Sciences, Arts, and Trades, a key work of Enlightenment thought. He wrote extensively on religion and atheism, philosophical materialism, art, literature, and education. He is of particular interest to libertarians for his opposition to censorship, colonialism, slavery, sexual restrictions, and religious intolerance. Often he received no credit for his efforts because many of his works were not published until after his death, many were anonymous, and the authorship of still others remained long in dispute.

Diderot was born in Langres, Champagne, and received a Jesuit education. Although he prepared for a degree in theology, he abandoned Catholicism early in life and embraced an open, often strident atheism. His 1749 Letter on the Blind expanded on the empiricist philosophy of John Locke and argued that all ideas must originate with the senses and that, by implication, neither innate ideas, nor God, nor divine revelation was real.

Diderot’s work earned him a stay in the Vincennes prison, an experience that solidified his hatred of censorship and arbitrary power. Although his most influential writings are in epistemology, metaphysics, and aesthetics, his political thought is likewise of great interest. Diderot used commentaries on both the ancient and contemporary worlds to expound a variety of ideas that have since become central to libertarian thinking. For example, in his Essay on the Life of the Philosopher Seneca, Diderot wrote,