This book stands in the tradition of past and current common sense philosophers, like Reid, Berkeley, Sidgwick, Moore, Conant, Slote, Bogdan, and Lemos, who defend common sense, yet it goes beyond their accounts by not only defending common sense but also considering what common sense means. Besides giving a historical exegesis of common sense in Thomas Reid and showing parallels in Austin, Searle, Moore, and Wittgenstein, common sense is also discovered in Hume’s An Enquiry Concerning the Principles of Morals and in Kant’s Critique of Pure Reason. It is made clear how far common sense generalizes, whether proverbs are a form of common sense, and whether common sense can be found in the common knowledge assumption in game theory. Also, folk psychology as a common sense psychology is discussed. In its account of common sense, this book draws on research from history of philosophy, philosophy of mind, and science, linguistics, and game theory to substantiate its position.