The philosopher Penelope Maddy is well-known for her pursuit of 'Second Philosophy', a form of naturalism that sees the methods of philosophy as indistinguishable from those of the empirical sciences. This volume collects eleven of her recent essays (five new and six reprinted), exploring a wide range of philosophical topics--from methodology, epistemology, and the philosophy of science, to the philosophies of logic, arithmetic, and higher mathematics. Though the topics vary widely, each essay bears in one way or another on the description, exploration, or application of Second Philosophy, revealing the underlying systematic character of Maddy's thought.The title essay traces the source of second-philosophical thinking to the 'natural philosophy' of the early modern period, when 'science' and 'philosophy' weren't separate disciplines; a companion essay, drawing second-philosophical morals for the realism/instrumentalism debate in the philosophy of science rounds out the opening section on philosophical method. The second section, on external world skepticism, is largely historical: an essay comparing the naturalistic credentials of Hume and Reid, then one each on Moore and Wittgenstein. A second-philosophical examination of debates over truth and reference, starring J. L. Austin, opens the section on language and logic, followed by a broad-brush description of historical landmarks in the philosophy of logic and an executive summary of the Second Philosopher's view. The concluding section on mathematics begins with an essay addressed to undergraduates on the ontology of number and another assessing the bearing of contemporary developmental psychology on the philosophies of logic and arithmetic. The concluding essay is an attempt to revive the often-ridiculed if-thenist position in the philosophy of mathematics.Maddy's second-philosophical essays offer new insight into long-standing questions in the philosophy of science, epistemology, the philosophies of language, logic, mathematics-all with an eye to the methodological themes that connect them.