175px|Opening page of The System of Nature. The System of Nature or, the Laws of the Moral and Physical World (Système de la Nature ou Des Loix du Monde Physique et du Monde Moral) is a work of philosophy by Paul-Henri Thiry, Baron d'Holbach (1723–1789). It was originally published under the name of Jean-Baptiste de Mirabaud, a deceased member of the French Academy of Science. D'Holbach wrote and published this book possibly with the assistance of Diderot but with the support of Jacques-André Naigeon anonymously in 1770, describing the universe in terms of the principles of philosophical materialism: the mind is identified with brain, there is no "soul" without a living body, the world is governed by strict deterministic laws, free will is an illusion, there are no final causes, and whatever happens takes place because it inexorably must. Most notoriously, the work explicitly denies the existence of God, arguing that belief in a higher being is the product of fear, lack of understanding, and anthropomorphism.