The Naturalist philosophy, though fragmented, is particularly suited to the literary exploration of a seemingly fated historical incident. First propounded by the French novelist Émile Zola, Naturalism usually involves the idea that unconscious motivations, influenced by social and environmental factors, lead people toward their inevitable ends. As such, the Mussel Slough Tragedy’s impression of determinism—that is, its grimly precise sequence of events and their catastrophic conclusion—naturally appealed to Norris. The tragedy supplied a proving ground for a literary philosophy proposing characters’ unavoidable ruination. At the same time, Norris’s determinism is decentralized; Where one character’s fate is clinched by their own unconscious appetites, another’s fate hinges on others’ motivations. Most often, though, fateful determinants’ loci are mixed. For example, while the Railroad is the novel’s supreme and despotic arbiter, the characters’ own primal impulses—lust, fear, pride, greed—have catalyzing power. Each character is a variation of the theme.

Naturalism, which draws from evolutionary models resembling Social Darwinism, posits that at the core of every human is a profoundly motivating base animalism to which anyone can revert. Annixter’s character is the most direct bodily representation of these urges. Although educated as a civil engineer, and clearly at home in the higher sphere of the intellect, he is undermined by seemingly inexplicable stomach issues (he clings comically to some sense of control by insisting upon his own cure, prunes, though they are inefficacious).