Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Logic. Definitions of logic, History of logic, Organon, Propositional calculus, Modal logic, Informal logic, Mathematical logic, Philosophical logic, Principle of bivalence, Is logic empirical?, Paradoxes of material implication, Paraconsistent logic, Metalogic, Logic puzzle, Mathematics, Table of logic symbols, Digital electronics, Truth, Reason