Introduction to Logic

Introduction to Logic

Introduction to Logic

Introduction to Logic


Introduction to Logic offers one of the most clear, interesting and accessible introductions to what has long been considered one of the most challenging subjects in philosophy. Harry Gensler engages students with the basics of logic through practical examples and important arguments both in the history of philosophy and from contemporary philosophy. Using simple and manageable methods for testing arguments, students are led step-by-step to master the complexities of logic.The companion LogiCola instructional program and various teaching aids (including a teacher's manual) are available from the book's website:


Logic is about reasoning—about going from premises to a conclusion. As we begin our study of logic, we need to get clearer on what logic is and why it’s important. We also need to learn some concepts (like “valid” and “argument”) that are central to the study of logic.

1.1 Logic

Logic can be defined as the analysis and appraisal of arguments. When you do logic, you try to clarify reasoning and separate good from bad reasoning. As you work through this book, you’ll examine philosophical reasoning on topics like free will and determinism, the existence of God, and the nature of morality. You’ll also study reasoning on backpacking, water pollution, football, Supreme Court decisions, and the Bible. You’ll come to see logic not as an irrelevant game with funny symbols, but rather as a useful tool to clarify and evaluate our reasoning—whether on everyday topics or on life’s deeper questions.

Why study logic? I can think of three main reasons. First, logic can be fun. Doing logic is like playing a game or doing puzzles; logic will challenge your thinking processes in new ways. The rigor of logical systems will likely fascinate you. Most people find logic enjoyable.

Second, logic can deepen your understanding of philosophy. Philosophy can be defined as reasoning about the ultimate questions of life. Philosophers ask questions like “Why accept or reject free will?,” “Can one prove or disprove God’s existence?,” and “How can one justify a moral belief?” If you don’t know any logic, you’ll have only a vague grasp of such issues; and you’ll lack the tools needed to understand and evaluate philosophical reasoning. If you’ve studied philosophy, you’ll likely recognize many of the pieces of philosophical reasoning in this book. If you haven’t studied philosophy, you’ll find this book a good introduction to the subject. In either case, you should get better at recognizing, understanding, and appraising philosophical reasoning.

Important terms (like “logic”) are introduced in bold type. Learn each such term and be able to give a definition. The Glossary at the end of the book has a collection of definitions.

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