This book is concerned chiefly with issues in epistemology, philosophical semantics and philosophy of science. It defends a causal-realist approach to theories and explanations in the natural sciences and a truth-based propositional semantics for natural language derived from various sources, among them unusually in this context the work of William Empson. It argues against various forms of anti-realist doctrine with regard to both the truth-claims of science and the construal of intentions, meanings and beliefs in the process of linguistic understanding. His book will be welcomed for its vigorous arguments and notable clarity of style. It will be of particular interest to teachers and students in philosophy, critical theory, science studies and the history of ideas.