Holbach is best known for The System of Nature (1770) and deservedly, since it is a clear and reasonably systematic exposition of his main ideas. His initial position determines all the rest of his argument. "There is not, there can be nothing out of that Nature which includes all beings." Conceiving of nature as strictly limited to matter and motion, both of which have always existed, he flatly denies that there is any such thing as spirit or a supernatural.