This book contains contributions from most members of the Research Group of the Complutense University of Madrid "Philosophy of Language, of Nature and of Science", the leading interdepartmental research group of the Faculty of Philosophy of this university. The book mainly includes research essays on these fields and aims to offer a panoramic view of some outstanding issues within those disciplines. The essays on Philosophy of Nature and of Science concern the sociology of scientific knowledge, the inference in the context of scientific discovery, the pragmatist view of science, some prominent contributions to the philosophy of biology and of chemistry as well as Wittgenstein's and Husserl's views on natural science. The essays on Philosophy of Language (and of mind) deal with important questions regarding the notions of reference, intentionality, mental content, the relations between certain conceptions of mental content and a priori knowledge and, on the historical side, the application of some of Leibniz's contributions on formal languages. Some of the essays have a more introductory character, others a more specialized one, but the whole book intends to provide the reader who is interested in the Philosophy of Language, of Nature and/or of Science, or in Philosophy in general, with appealing contributions worthy of consideration.