Herbert Spencer (1820-1903), British social philosopher, often regarded as one of the first sociologists. Born in Derby, England, Spencer was mainly self-educated. His early influences included the utilitarian philosophy of Jeremy Bentham and an early theory of evolution developed by the French naturalist Jean-Baptiste Lamarck. See also Thematic Essay: British Political and Social Thought.

In 1850 Spencer published Social Statics, a work in which he stressed the importance of individual freedom and the inevitability of human progress. In Principles of Psychology (1855) Spencer wrote that all organic matter originates in a unified state and that individual characteristics gradually develop through evolution. The evolutionary progression from simple to more complex and diverse states was an important theme in most of Spencer's later works. In A System of Synthetic Philosophy (1860) Spencer outlined a plan for a comprehensive system of philosophy, based on evolution, that would embrace and integrate all existing fields of knowledge. The initial installment in this project, First Principles, appeared in 1862. Later works in the series include Principles of Biology (2 volumes, 1864-1867), Principles of Sociology (3 volumes, 1876-1896), and Principles of Ethics (2 volumes, 1892-1893).

After Charles Darwin published On the Origin of Species in 1859, Spencer embraced Darwin's theory of natural selection. Spencer was an influential proponent of social Darwinism, an application of Darwin's theory to human societies. The theory of natural selection holds that only the most well-adapted individuals in a population will survive and reproduce. Because these successful individuals pass on their adaptive advantage to their offspring, the cumulative effect of this process over many generations is the adaptation of the entire population to its environment. Spencer coined the phrase “survival of the fittest” to describe the competition among human individuals and groups. He argued that human progress resulted from the triumph of more advanced individuals and cultures over their inferior competitors. Wealth and power were seen as signs of inherent “fitness,” while poverty was taken as evidence of natural inferiority. In the late 19th and early 20th centuries, social Darwinism was used to argue for unrestrained economic competition and against aid to the “unfit” poor. The theory was also used to justify racist and imperialist policies in Europe and the United States.

When social Darwinist ideas fell from favor in the early 20th century, Spencer's reputation as a philosopher and social theorist declined. Nonetheless, his ambitious attempt to systematize all knowledge within the framework of modern science, and especially in terms of evolution, earned him a place among the notable thinkers of the late 19th century. Other works by Spencer include The Man Versus the State (1884) and Essays: Scientific, Political, and Speculative (3 volumes, 1891).