Since its original publication in 1979, The Possibility of Naturalism has been one of the most influential works in contemporary philosophy of science and social science. It is one of the cornerstones of the critical realist position, which is now widely seen as offering perhaps the only viable alternative to positivism and post positivism. This fourth edition contains a new foreword from Mervyn Hartwig, who is founding editor of the Journal of Critical Realism and editor and principal author of the Dictionary of Critical Realism.