Paul-Henri Thiry, Baron d'Holbach (1723–89) was a French philosopher during the Enlightenment. He was an author, and one of the Encyclopedists (French Encyclopédie) who advocated naturalistic and materialistic ideas. He was an opponent of Christianity and religion. His most well known work was Système de la nature (The System of Nature) published in 1770, which was first published under the name of Mirabaud.  He was an early advocate of atheism in Europe.