Recent debates in philosophy of science and epistemology are characterized by some strong oppositions, such as those between instrumentalism and scientific realism, methodological anarchism and critical rationalism, historical contextualism and metaphysical realism, naturalism and normativism. By means of a close interaction between historical research and theoretical perspective, this book aims to develop a "third way" between absolutism and radical relativism. This conception is called "positive" because it is linked to the basic features of the esprit positif: empiricism, moderate epistemic relativism, and non-metaphysical objectivism. This book revives the early 20th-century controversy between the immanent and transcendent conception of the object of knowledge, and offers a new interpretation of the relationships between logical positivism, Kantian thought, and conventionalist philosophy of science. According to the author, such a "positive philosophy" is able to counter the "conversational" and post-modern attacks on objectivity and truth.The book is aimed at libraries and research workers in epistemology, philosophy of science, metaphysics, history of philosophy and history of science, and philosophy of language.