and the last of the 251 copies of its first edition were not sold until June 1861. Spencer's interest in psychology derived from a more fundamental concern which was to establish the universality of natural law. In common with others of his generation, including the members of Chapman's salon, he was possessed with the idea of demonstrating that it was possible to show that everything in the universe – including human culture, language, and morality – could be explained by laws of universal validity. This was in contrast to the views of many theologians of the time who insisted that some parts of creation, in particular the human soul, were beyond the realm of scientific investigation. Comte's Système de Philosophie Positive had been written with the ambition of demonstrating the universality of natural law, and Spencer was to follow Comte in the scale of his ambition. However, Spencer differed from Comte in believing it was possible to discover a single law of universal application which he identified with progressive development and was to call the principle of evolution. In 1858 Spencer produced an outline of what was to become the System of Synthetic Philosophy. This immense undertaking, which has few parallels in the English language, aimed to demonstrate that the principle of evolution applied in biology, psychology, sociology (Spencer appropriated Comte's term for the new discipline) and morality. Spencer envisaged that this work of ten volumes would take twenty years to complete; in the end it took him twice as long and consumed almost all the rest of his long life. Despite Spencer's early struggles to establish himself as a writer, by the 1870s he had become the most famous philosopher of the age. His works were widely read during his lifetime, and by 1869 he was able to support himself solely on the profit of book sales and on income from his regular contributions to Victorian periodicals which were collected as three volumes of Essays. His works were translated into German, Italian, Spanish, French, Russian, Japanese and Chinese, and into many other languages and he was offered honours and awards all over Europe and North America. He also became a member of the Athenaeum, an exclusive Gentleman's Club in London open only to those distinguished in the arts and sciences, and the X Club, a dining club of nine founded by T.H. Huxley that met every month and included