According to Sire, at its heart, nihilism is it “the negation of everything—knowledge, ethics, beauty, reality” (84). Nihilism is more a feeling or attitude than a consistent philosophy, he believes. Although the majority of people have never felt the despair of nihilism, it has been an influential worldview in the 20th and 21st centuries, affecting art and literature and social movements, and as such it is important to come to an understanding of it.

Nihilism is the “natural child” or direct consequence of naturalism pushed to its limits. This seems paradoxical at first glance, because naturalism seems to assure human beings of their worth and self-determination within the universe. Sire argues that there are three factors, or “bridges”—logical implications inherent in naturalism—that led gradually to nihilism. They have to do respectively with metaphysics, epistemology, and ethics.

The first bridge (the metaphysical) is that of necessity and chance. In positing that (1) matter is all there is and is eternal and (2) the universe is ruled by a closed system of cause and effect, naturalism implies that human beings are only complex machines. This in turn implies that human beings lack freedom of choice; our actions are determined by evolution, biological and genetic processes, and other natural causes.