 Atheism. Atheism is more present in the French Enlightenment than elsewhere. In the writings of Denis Diderot, atheism is partly supported by an expansive, dynamic conception of nature. According to the viewpoint developed by Diderot, we ought to search for the principles of natural order within natural processes themselves, not in a supernatural being. Even if we don’t yet know the internal principles for the ordering and development of natural forms, the appeal to a transcendent author of such things is reminiscent, to Diderot’s ear, of the appeal to Aristotelian “substantial forms” that was expressly rejected at the beginning of modern science as explaining nothing. The appeal to a transcendent author does not extend our understanding, but merely marks and fixes the limits of it. Atheism (combined with materialism) in the French Enlightenment is perhaps most identified with the Baron d’Holbach, whose System of Nature (1770) generated a great deal of controversy at the time for urging the case for atheism explicitly and emphatically. D’Holbach’s system of nature is strongly influenced by Diderot’s writings, though it displays less subtlety and dialectical sophistication. Though most Enlightenment thinkers hold that morality requires religion, in the sense that morality requires belief in a transcendent law-giver and in an after-life, d’Holbach (influenced in this respect by Spinoza, among others) makes the case for an ethical naturalism, an ethics that is free of any reference to a supernatural grounding or aspiration. Like Helvétius before him, d’Holbach presents an ethics in which virtue consists in enlightened self-interest. The metaphysical background of the ethics he presents is deterministic materialism. The Prussian enlightened despot, Frederick the Great, famously criticizes d’Holbach’s book for exemplifying the incoherence that troubles the Enlightenment generally: while d’Holbach provides passionate moral critiques of existing religious and social and political institutions and practices, his own materialist, determinist conception of nature allows no place for moral “oughts” and prescriptions and values.