Informal Fallacies

Dean Da vee

Deductive Logic

Alex LeBrun

Download Chapter on Informal Fallacies
©Dean Da Vee CC BY-NC-ND 4.0, 2026

Download Chapter on Deductive Logic
©Alex LeBrun CC BY-NC-ND 4.0, 2026

This chapter introduces students to common informal fallacies. Students learn to identify fallacies of relevance, such as ad hominem, strawman, red herring, whataboutism, and appeal to unqualified authority or popularity. They also learn to identify fallacies of presumption, including begging the question, false cause, slippery slope, hasty generalization, argument from ignorance, and false dichotomy. Throughout, real-world examples help students recognize these patterns in everyday reasoning, political discourse, and public debate.

This chapter introduces students to the basics of deductive logic. Students learn to represent sentences using letters and logical connectives such as negation, conjunction, disjunction, conditional, or biconditional, and practice translating everyday arguments into symbolic form. The chapter then covers truth tables and finally, students apply truth tables to three key logical concepts: equivalence, consistency, and validity.

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Chancellor's Office
California State University

AI Educational Innovation Challenge
2025-2026

Critical Thinking and AI Group

admin@thephilosophynotebook.com

California Polytechnic State University

Philosophy Department

F. Fernflores (PI)