Tuesday, September 22, 2009

Book Review (5): The Ultimate Proof of Creation

Chapter 7 is called “Logical Fallacies – Part 1,” and it is the first of 2 chapters on the topic. Readers may think this portion of the book to be a recap of a course often taken the first year of college, “Introduction to Logic.” But it’s a valuable refresher for those readers, and it’s an even more important lesson for people unfamiliar with the framework of logical argumentation. Lisle defines terms such as proposition, conclusion, argument, and premise and discusses various kinds of logic (formal and informal, as well as inductive and deductive arguments). Lisle introduces and illustrates the practicality of several informal logical fallacies, such as ambiguity (equivocation and reification), presumption (hasty generalization, sweeping generalization, bifurcation, begging the question, question-begging epithet, complex question, the “no true Scotsman fallacy,” special pleading, false analogy, false cause, and slippery slope), and relevance (genetic fallacy, ad hominem, faulty appeal to pity, appeal to mob, appeal to authority, appeal to one, appeal to many/majority, appeal to ignorance, appeal to fear, irrelevant thesis, and straw man). While I’d love to go into more detail on these, Lisle does a better job than I could, so just read the book!

Chapter 8, the conclusion to chapter 7, is called “Logical Fallacies – Part 2,” and Lisle discusses the topic of formal logic in basic, yet fairly complete detail. He first covers formal deductive logic, defining syllogism, categorical logic, and propositional logic. Sticking to the topic of propositional logic, the author first mentions refutation of such arguments by logical analogy, and then he covers types of propositional arguments, including disjunctive syllogisms and mixed hypothetical syllogisms (modus ponens, or affirming the antecedent, and modus tollens, or denying the consequent). A disjunctive syllogism would have two premises (either “p” or “q”, and “not p”) and a conclusion (therefore “q”), where both premises are absolute. The first type of mixed hypothetical syllogism (modus ponens, affirming the antecedent) would also have two premises (if “p” then “q”, and “p”) and a conclusion (therefore “q”), but the difference is that the first premise is hypothetical ("if" instead of "either", making for a mixed argument. Likewise the second type of mixed hypothetical syllogism (modus tollens, denying the consequent) is similar, but where the first type affirms the front half of the first premise with the second premise (“p”), the second type denies the back half of the first premise with the second premise (“not q”). The logic would flow with two premises (if “p” then “q”, and “not q”) and a necessary conclusion (therefore, not “p”).

After covering the basic types of formal logic, Lisle discusses two ways that formal logical arguments such as modus ponens and modus tollens are misused and deemed invalid – affirming the consequent and denying the antecedent. In the first, the premises could be valid (if “p” then “q”, and “q”), but the conclusion (therefore “p”) may not logically follow. Lisle’s example relates to the weather. “If it is snowing, then it must be cold outside. It is cold outside. Therefore, it must be snowing.” Hopefully, you can see the error. In the second, the premises could be valid (if “p” then “q”, and “not p”), but the conclusion (therefore “not q”) may not logically follow. Again Lisle’s illustration says, “If it is snowing, then it must be cold outside. It is not snowing. Therefore, it is not cold outside.” Again, hopefully you can see the error.

Lisle wraps up chapter 8 by mentioning valid, formally logical arguments that are unsound, based on faulty premises, and enthymemes, which are valid arguments with unstated propositions that must be reformulated or clarified to make the arguments fit into a formal logic formula. Most conversational arguments probably come in the form of enthymemes. After a brief reminder of the importance of consistency in logical argumentation, Lisle concludes by saying, “The ability to recognize and expose fallacies and false premises is a crucial but often overlooked part of Christian apologetics.” Amen.

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