The Thinker's Library was a series of 140 small hardcover books published between 1929 and 1951 for the Rationalist Press Association by Watts & Co., London, a company founded by the brothers Charles and John Watts. The series was launched at the time when Watts & Co. was being run by Charles Albert Watts. A member of the company's board of directors, Archibald Robertson, took an active interest in setting up the series and it was he who suggested the series' name. The Thinker's Library consisted of a selection of essays, literature, and extracts from greater works by various classical and contemporary humanists and rationalists, continuing in the tradition of the Renaissance. Many of the titles were cheap reprints of classic books, aimed at a mass audience. Catalogue of titles Each volume consists of an eponymous essay sometimes followed by a collection of related essays by the same author, or an introductory extract from a greater work by that author. Any deviation from this format will be self-explanatory from the title. All foreign language texts were published in the English language. First and Last Things by H. G. Wells Education: Intellectual, Moral, and Physical by Herbert Spencer The Riddle of the Universe by Ernst Haeckel Humanity's Gain from Unbelief, and Other Selections from the Works of Charles Bradlaugh (1929) On Liberty by John Stuart Mill A Short History of the World by H. G. Wells The Autobiography of Charles Darwin by Charles Darwin The Origin of Species by Charles Darwin Twelve Years in a Monastery by Joseph McCabe History of Modern Philosophy by A. W. Benn (1930) Gibbon on Christianity – chapters 15 and 16 of Edward Gibbon's Decline and Fall of the Roman Empire (1930) The Descent of Man – Part 1 and the concluding chapter of Part 3, by Charles Darwin (1930) History of Civilization in England – Vol. I, by Henry Thomas Buckle Anthropology – Vol. I, by Sir Edward B. Tylor Anthropology – Vol. II, by Sir Edward B. Tylor Iphigenia – Two plays, by Euripides, translated by C. B. Bonner Lectures and Essays by Thomas Henry Huxley The Evolution of the Idea of God by Grant Allen An Agnostic's Apology, and Other Essays by Sir Leslie Stephen (March 1931) The Churches and Modern Thought by Vivian Phelips Penguin Island by Anatole France The Pathetic Fallacy by Llewelyn Powys Historical Trials (A Selection) by Sir John