The survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called natural selection, or the preservation of favored races in the struggle for life.
Source: Principles of Biology, pt 3, ch. 12, 1864-1867.
-- Herbert Spencer, (Apr 27 1820-1903), English naturalist, philosopher; He applied Darwin's theory of evolution to philosophy and popularized the idea of survival of the fittest; wrote Principles of Sociology, 1876-96.