Herbert Spencer (1820-1903) was a major thinker in 19th century philosophy and sociology. He drew heavily on the work of Charles Darwin, attempting to apply the laws of natural selection to human societies. Spencer coined the term "survival of the fittest," believing that the richer classes and "superior races" were destined to beat out the poorer classes and "inferior races" in the struggle for survival. His beliefs became very popular among academics and business leaders in late 19th century England, Germany, and the United States. In essence Spencer provided an intellectual justification for the wide disparities in wealth in modern industrial society, as well as for turn of the century European and American imperialism.

Spencer greatly influenced Francis Galton, the originator of eugenics. While Spencer died before the eugenics movement gained widespread popularity, his ideas about the natural inequalities between different groups and individuals proved important to the formulation of eugenic ideology.