Herbert Spencer was a British social philosopher who applied his personal conception of evolution to many other fields, from the origin of the solar system to economics. He first used the term in his book "Principles of Biology", published in 1864. In that book (vol 1 p444) he wrote: "This 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 favoured races in the struggle for life".