R.G. Collingwood (1889-1943) was a British philosopher and practicing archaeologist, best known for his work in aesthetics and the philosophy of history. During the 1950s and 1960s, his philosophy of history, in particular, occupied center stage in the debate concerning the nature of explanation in the social sciences and whether they are ultimately reducible to explanations in the natural sciences. Primarily through the interpretative efforts of W. H. Dray, Collingwood's work in the philosophy of history came to be seen as providing a powerful antidote to Carl Hempel's claim for methodological unity. Collingwood authored two of the most important treatises in meta- philosophy written in the first half of the twentieth century: An Essay on Philosophical Method (1933) and An Essay on Metaphysics (1940). They both contain sustained discussions of the role and character of philosophical analysis and why the method of philosophy is distinct from and irreducible to the methods of the natural and exact sciences. He is often described as one of the British Idealists, although this label fails to capture his distinctive kind of idealism, which is conceptual rather than metaphysical. In his correspondence with Gilbert Ryle, Collingwood explicitly rejected the label "idealist" because he did not endorse the arch-rationalist assumptions that shaped much British idealism at the end of the nineteenth and early twentieth centuries, and consequently did not wish to be identified with it.