The System of Nature

Published in 1770, The System of Nature was the work of Paul-Henri Thiry, Baron d’Holbach, though it initially appeared under the name of the deceased academician Jean-Baptiste de Mirabaud. D’Holbach wrote the book anonymously, possibly with help from Denis Diderot and with support from Jacques-André Naigeon. The work presents a universe governed entirely by philosophical materialism: the mind is simply the brain, no soul exists apart from a living body, and strict deterministic laws rule all events. Free will is dismissed as an illusion, final causes are rejected, and everything happens because it must.

The book explicitly denies God’s existence, arguing that belief in a higher being arises from fear, ignorance, and anthropomorphism. Though not a scientist, d’Holbach was scientifically literate and grounded his philosophy in the knowledge of his era, citing John Needham’s experiments as evidence that life could arise spontaneously without divine intervention. A key distinction is drawn between mythology, which benignly conveys law and order to the masses, and theology, which separates nature from its power by personifying that power outside nature, making theology a uniquely harmful force.

The work was considered extremely radical, prompting refutations from figures such as the theologian Nicolas-Sylvestre Bergier, Voltaire, and even Frederick the Great, who may have been motivated by the book’s attacks on monarchy as well as religion. Diderot enthusiastically endorsed it, and Percy Bysshe Shelley became an ardent atheist after reading it, later translating it into English. Goethe, however, recoiled from its grim, corpse-like vision, both in his youth and old age. Despite such reactions, Voltaire noted its popularity among scholars, the ignorant, and women.