During the past few decades, a radical shift has occurred in how philosophers conceive of the relation between science and philosophy. A great number of analytic philosophers have adopted what is commonly called a "naturalistic" approach, arguing that their inquiries ought to be in some sense continuous with science. Where early analytic philosophers often relied on a sharp distinction between science and philosophy--the former an empirical discipline concerned with fact, the latter an a priori discipline concerned with meaning--philosophers today largely follow Willard Van Orman Quine (1908-2000) in his seminal rejection of this distinction. Sander Verhaegh here offers a comprehensive study of Quine's groundbreaking naturalism. Building on Quine's published corpus as well as a wealth of unpublished letters, notes, lectures, papers, proposals, and annotations from the Quine archives, Verhaegh aims to reconstruct both the nature and the development of his naturalism. As such, Working from Within aims to contribute to the rapidly developing historiography of analytic philosophy, and to provide a better, historically informed, understanding of what is philosophically at stake in the contemporary naturalistic turn. Transcriptions of five unpublished papers, letters, and notes are included in the appendix.