David Kellogg Lewis (1941-2001) was an American philosopher who taught at Princeton University and the University of California, Los Angeles and contributed to metaphysics, philosophy of mind, philosophy of language, philosophy of mathematics, philosophy of science, decision theory, epistemology, meta-ethics, and aesthetics. Lewis's papers include over four decades of his correspondence with other philosophers and scholars, including David M. Armstrong, J. J. C. Smart, Frank Jackson, D. H. Mellor, M. J. Cresswell, Allen Hazen, John Bigelow, and others, as well as drafts of his articles, books, reviews, and unpublished writings with related correspondence, his undergraduate and graduate student papers and class notes, research materials from his time at the Hudson Institute, photographs of Lewis with friends and fellow philosophers, a group of files kept by the Australian philosopher David M. Armstrong regarding Lewis, papers of Stephanie R. Lewis, and family papers.