Abstract: Many philosophers these days consider themselves naturalists, but it's doubtful any two of them intend the same position by the term. This book describes and practices a particularly austere form of naturalism called ‘Second Philosophy’. Without a definitive criterion for what counts as ‘science’ and what doesn't, Second Philosophy can't be specified directly — ‘trust only the methods of science!’ or some such thing — so the book proceeds instead by illustrating the behaviors of an idealized inquirer called here the ‘Second Philosopher’. This Second Philosopher begins from perceptual common sense and progresses from there to systematic observation, active experimentation, theory formation and testing, working all the while to assess, correct and improve methods along the way. ‘Second Philosophy’ is then the result of the Second Philosopher's investigations. This book delineates the Second Philosopher's approach by tracing reactions to various familiar skeptical and transcendental views (Descartes, Kant, Carnap, late Putnam, van Fraassen), comparing methods to those of other self-described naturalists (especially Quine), and examining a prominent contemporary debate (between disquotationalists and correspondence theorists in the theory of truth) to extract a properly second-philosophical line of thought. The book then undertakes to practice Second Philosophy in its reflections on the ground of logical truth, the methodology, ontology, and epistemology of mathematics, and the general prospects for metaphysics naturalized.

Keywords: naturalism, philosophy of logic, philosophy of mathematics, metaphysics naturalized, second philosophy, skepticism, truth and reference