CHAPTER 5
Understanding Logic and Recognizing Logical Fallacies

The word logic comes from the Greek word logos, roughly translated as “word,” “thought,” “principle,” or “reason.” Logic is concerned with the principles of correct reasoning. By studying logic, you learn the rules that determine the validity of arguments. In other words, logic enables you to tell whether a conclusion correctly follows from a set of statements or assumptions.

Why should you study logic? One answer is that logic enables you to make valid points and draw sound conclusions. An understanding of logic also enables you to evaluate the arguments of others. When you understand the basic principles of logic, you know how to tell the difference between a strong argument and a weak argument—between one that is well reasoned and one that is not. This ability can help you cut through the tangle of jumbled thought that characterizes many of the arguments you encounter daily—on television, radio, and the Internet; in the press; and from friends. Finally, logic enables you to communicate clearly and forcefully. Understanding the characteristics of good arguments helps you to present your own ideas in a coherent and even compelling way.

Specific rules determine the criteria you use to develop (and to evaluate) arguments logically. For this reason, you should become familiar with the basic principles of deductive and inductive reasoning —two important ways information is organized in argumentative essays. (Keep in mind that a single argumentative essay might contain both deductive reasoning and inductive reasoning. For the sake of clarity, however, we will discuss them separately.)