Exploring philosophy through detailed argument analyses of texts by philosophers from Plato to Strawson using a novel and transparent method of analysis. The best way to introduce students to philosophy and philosophical discourse is to have them read and wrestle with original sources. This textbook explores philosophy through detailed argument analyses of texts by philosophers from Plato to Strawson. It presents a novel and transparent method of analysis that will teach students not only how to understand and evaluate philosophers' arguments but also how to construct such arguments themselves. Students will learn to read a text and discover what the philosopher thinks, why the philosopher thinks it, and whether the supporting argument is good. Students learn argument analysis through argument diagrams, with color-coding of the argument's various elements-conclusion, claims, and indicator phrases. (An online mini-course in argument diagramming and argument diagramming software are both freely available online.) Each chapter ends with exercises and reading questions. After a general introduction to philosophy and logic and an explanation of argument analysis, the book presents selections from primary sources, arranged by topics that correspond to contemporary debates, with detailed analysis and evaluation. These topics include philosophy of religion, epistemology, theory of mind, free will and determinism, and ethics; authors include Aristotle, Aquinas, Descartes, Hume, Kant, Ryle, Fodor, Dennett, Searle, and others. What Is the Argument? not only introduces students to great philosophical thinkers, it also teaches them the essential skill of critical thinking.