Robin George Collingwood (1889-1943) was both a British philosopher and a practising historian specialized in the archaeology and history of Roman Britain. His most important contributions to philosophy were on philosophy of history and on aesthetics. In both these areas R. G. Collingwood’s reflection was based on his own experience as a historian and as an artist respectively, although only in the first field he was a first class figure. As a philosopher of history, he defended the superiority of history as a form of knowledge with respect to natural sciences, and its methodological independence from them. As a philosopher of art, he understood art as the expression of emotion in the language of imagination. He also made top contributions in meta-philosophy, metaphysics and political philosophy. Collingwood is usually considered to be a British Idealist, although such categorization is polemic because he himself denied it in different places.
Collingwood’s first important work was published in 1924. Its title was Speculum Mentis (Or the Map of Knowledge), and can be considered as his first systematic attempt at describing our complete experience of the world. A year later, he published Outlines of a Philosophy of Art, where he proposed to consider art as an imaginative activity that attempts to achieve beauty and by which we enjoy it. From here he moved on to the consideration of the place and methodology of philosophy as a distinct form of knowledge in An Essay on Philosophical Method, published in 1933. Five years later, in 1938, he returned once again to the philosophy of art, in The Principles of Art, where he substantially revised and expanded his original definition of art, considering it now as the expression of emotion in the language of imagination. Around this time, Collingwood was conscious of the seriousness of the illness that would end his life, and published An Autobiography in 1939 as his philosophical testament. In the last years of his life, he managed to prepare and publish An Essay on Metaphysics (1940) where he considered Metaphysics to be the study of absolute presuppositions and not the study of being; and The New Leviathan (1942) which is more than a contribution to the war effort, as Collingwood himself considered it, and can be better viewed both as a complete summary of more than twenty years of philosophical work, and as his last attempt at providing a coherent explanation of mankind (individual, society, civilization and barbarism). Finally and although Collingwood’s reflection on the philosophy of history was a constant throughout his life, he didn’t publish any major work during it and his views are scattered in many articles. Following his own plans but after his death and both from the materials he published and from the ones he left unpublished, his ideas on the subject can be studied in The Idea of History, Essays on the Philosophy of History, and The Principles of History.
If you are interested in his philosophy, I am the editor of R. G. Collingwood’s category in philpapers.org. There you will find this same introduction, besides an almost complete bibliography (primary and secondary sources).