social Darwinism
the now discredited theory that social relations develop according to the principles of natural selection advanced by Charles Darwin. As articulated by Herbert Spencer and others, the theory proposed that societies evolve through survival of the fittest, the fittest being defined as those with wealth, power, and “natural” superiority in the struggle for existence. With its legitimizing of social, economic, and racial inequality, social Darwinism became a major ideological vehicle for justifying laissez-faire economics, imperialism, and eugenics in the late 19th and early 20th centuries.