This work is an introduction to informal and formal logic. It covers what is usually taught in the first term of a two-term sequence in logic at community colleges and at four-year colleges and universities. Following treatment of the nature of argument, this book distinguishes induction from deduction. The book then covers how to fill out argument fragments (or enthymemes) and how to recognize, as well as how to avoid constructing, deceptive or mistaken arguments (informal fallacies). Aristotle's class logic is canvassed, specifying rules for constructing valid arguments, and identifying formal fallacies committed when these rules are broken. Boole's modifications of class logic and the formal system are also introduced. Under the heading of the formal system, truth trees, the truth table method for determining validity, and finally, proof construction are all covered. The section on proof construction walks students through the process of building a demonstration in logic.