From The Art and Popular Culture Encyclopedia
Spencer developed an all-embracing conception of evolution as the progressive development of the physical world, biological organisms, the human mind, and human culture and societies. The lifelong bachelor contributed to a wide range of subjects, including ethics, religion, politics, philosophy, biology, sociology, and psychology.
He is best known for coining the phrase, "survival of the fittest," which he did in Principles of Biology (1864), after reading Charles Darwin's The Origin of Species. This term strongly suggests natural selection, yet as Spencer extended evolution into realms of sociology and ethics, he made use of Lamarckism rather than natural selection.