This project will provide a linked series of inquiries into the way professional biologists, philosophers, historians, and others, beginning in the second half of the twentieth-century, developed the shared disciplinary space today referred to as ‘the philosophy of biology’. The narrative focuses on North America and (to a more limited extent) the UK and continental Europe in the years 1959 to 2009 – roughly, the period spanning the hundredth and hundred-and-fiftieth anniversary of Charles Darwin’s The Origin of Species. Debates between key players such as Ernst Mayr, Marjorie Grene, David Hull, Michael Ruse, Mary Williams, William Wimsatt, and Richard Lewontin are approached both from a philosophical perspective focused on the cogency of arguments and positions, and from historical perspectives that set these arguments and positions within larger institutional and intellectual-historical contexts. This combination of philosophical and historical methodologies supports a three-part investigation of disciplinary symbioses between biological, philosophical, and historical disciplines during the period in question; constitutive tensions between positions and methodologies defended by the study’s historical actors (for example: between reductionism and organicism; between positivism and historicism; and between functionalism and formalism); and branching lineages between traditions associated with competing positions and methodologies, which connect this history both with what came before and with the composition and structure of the philosophy of biology today.