How did Herbert Spencer's ideas affect Theodore Dreiser's view of human behavior?

Theodore Dreiser’s adoption of Herbert Spencer’s philosophical speculations profoundly shaped his naturalistic view of human behavior. After reading Spencer’s works in 1894, Dreiser concluded that human beings are essentially helpless, driven by instincts and powerful social forces that remain beyond their individual control.12

This perspective led Dreiser to perceive human society as an unequal, often harsh contest between the strong and the weak. Influenced by Spencer’s broader evolutionary theories—which suggested that principles like natural selection and the "survival of the fittest" apply to individuals and social classes—Dreiser’s novels frequently depicted characters struggling against indifferent environmental and material pressures.134

By replacing Victorian notions of propriety with an unflinching presentation of reality, Dreiser used these Spencerian insights to explore the complexities of human ambition, moral ambiguity, and the often-tragic consequences of life in a rapidly industrializing society.25