The Muirhead Library of Philosophy was an influential series which published some of the best writings of twentieth century philosophy. The original programme was drawn up by John Muirhead and published in Erdmann's History of Philosophy in 1890. This statement was published in slightly altered form in subsequent volumes:"The Muirhead Library of Philosophy was designed as a contribution to the History of Modern Philosophy under the heads: first of Different Schools of Thought — Sensationalist, Realist, idealist, Intuitivist; secondly of different Subjects — Psychology, Ethics, Political Philosophy, Theology. While much had been done in England in tracing the course of evolution in nature, history, economics, morals and religion, little had been done in tracing the development of thought on these subjects. Yet 'the evolution of opinion is part of the whole evolution'."