Updated: January 24, 2020

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updated: May 13, 2022

Logical Reasoning

Bradley H. Dowden

Philosophy Department California State University Sacramento

Sacramento, CA 95819 USA

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Preface

Copyright

? 2011, 2020 by Bradley H. Dowden This book Logical Reasoning by Bradley H. Dowden is licensed under a Creative Commons AttributionNonCommercial-ShareAlike CC BY-NC-SA. This license lets others remix, tweak, and build upon your work noncommercially, as long as they credit you and license their new creations under the identical terms. An earlier version of the book was published on paper by Wadsworth Publishing Company, Belmont, California USA in 1993 with ISBN number 0-534-17688-7. When Wadsworth decided no longer to print the book, they returned their publishing rights to the original author, Bradley Dowden. The current version has been significantly revised. The current online version is 508-compliant for people with disabilities. If you would like to suggest changes to the text, the author would appreciate your writing to him at dowden@csus.edu.

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Praise

Comments on the earlier 1993 paper edition, published by Wadsworth Publishing Company, which is owned by Cengage Learning:

"There is a great deal of coherence. The chapters build on one another. The organization is sound and the author does a superior job of presenting the structure of arguments. "

David M. Adams, California State Polytechnic University

"These examples work quite well. Their diversity, literacy, ethnic sensitivity, and relevancy should attract readers."

Stanley Baronett. Jr., University of Nevada Las Vegas

Far too many authors of contemporary texts in informal logic ? keeping an eye on the sorts of arguments found in books on formal logic ? forget, or underplay, how much of our daily reasoning is concerned not with arguments leading to truth-valued conclusions but with making choices, assessing reasons, seeking advice, etc. Dowden gets the balance and the emphasis right.

Norman Swartz, Simon Fraser University

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Acknowledgments

The following friends and colleagues deserve thanks for their help and encouragement with this project: Clifford Anderson, Hellan Roth Dowden, Louise Dowden, Robert Foreman, Richard Gould, Kenneth King, Marjorie Lee, Elizabeth Perry, Heidi Wackerli, Perry Weddle, Tiffany Whetstone, and the following reviewers: David Adams, California State Polytechnic University; Stanley Baronett, Jr., University of Nevada-Las Vegas; Shirley J. Bell, University of Arkansas at Monticello; Phyllis Berger, Diablo Valley College; Kevin Galvin, East Los Angeles College; Jacquelyn Ann Kegley, California State University-Bakersfield; Darryl Mehring, University of Colorado at Denver; Dean J. Nelson, Dutchess Community College; James E. Parejko, Chicago State University; Robert Sessions, Kirkwood Community College; and Stephanie Tucker, California State University Sacramento. Thinking and writing about logical reasoning has been enjoyable for me, but special thanks go to my children, Joshua, 8, and Justine, 3, for comic relief during the months of writing. This book is dedicated to them.

This book is dedicated to my wife Hellan whose good advice has improved the book in many ways.

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Table of Contents

Preface..........................................................................................................................................................ii Copyright ................................................................................................................................................ii Praise .......................................................................................................................................................iii Acknowledgments ................................................................................................................................iv

Table of Contents .......................................................................................................................................v C H A P T E R 1 How to Reason Logically ........................................................................................ 1

Facing a Decision as a Critical Thinker ............................................................................................... 2 Advice for Logical Reasoners ............................................................................................................... 5 Examples of Good Reasoning............................................................................................................. 15 Review of Major Points ....................................................................................................................... 19

Glossary ............................................................................................................................................. 20 Exercises ............................................................................................................................................ 20 C H A P T E R 2 Claims, Issues, and Arguments............................................................................ 25 What is a Statement?............................................................................................................................ 25 What is an Argument?......................................................................................................................... 27 What is the Issue?................................................................................................................................. 30 What is a Proof?.................................................................................................................................... 33 Indicators............................................................................................................................................... 34 Premise Indicators............................................................................................................................ 36 Conclusion Indicators...................................................................................................................... 36 Discount Indicators.......................................................................................................................... 40 Rewriting Arguments in Standard Form.......................................................................................... 41 Conditionals and the Word If ............................................................................................................. 42 Deductively Valid and Inductively Strong....................................................................................... 46 Uncovering Implicit Premises ............................................................................................................ 48 Locating Unstated Conclusions ......................................................................................................... 53 Detecting Obscure Argumentation ................................................................................................... 56 Descriptions and Explanations .......................................................................................................... 60 Review of Major Points ....................................................................................................................... 68

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