LOGIC AND CRITICAL THINKING

1. LOGIC AND CRITICAL THINKING The Way to the Good Reasoning and Making Good Argument 時間：92年10月18日 地點：東吳大學外雙溪 主講：米建國 東吳大學哲學系

2. What Is Critical Thinking? • Think it twice: Don’t take things for granted so easily. • Always ask the why-question: Try to find out the reason (the premises) why certain claim (the conclusion) can be supported. • Examine and evaluate the relationship between the reasons and the claim.

3. Paradoxes • Self-defeating paradox: The concept of “all powerful” God • Zeno’s paradox: An apparently unacceptable conclusion derived by apparently acceptable reasoning from apparently acceptable premises • Semantic paradox: The liar’s paradox • The lawyer’s paradox • Prisoner’s dilemma • Russell’s paradox (Barber’s paradox) • The lottery paradox

4. What is logic? • Logic is not an empirical science • Formal or informal science • Logic v.s.Psychology: 1. The Laws of Thinking 2. The Science of Reasoning 3. The Science of Argument • The study of the methods and principles used to distinguish good (correct) from bad (incorrect) reasoning or argument. • The way to the good reasoning (making good argument) and critical thinking

5. What Is an Argument? • An argument is the fundamental structure of the reasoning. • An argument consists of premises and conclusion. • An argument is used to provide reasons for supporting some claim or proposal. • Logic aims to the study of the various forms of argument. • The ultimate goal of logic is to evaluate arguments.

6. The Standard Form of Argument • P = premise, C = conclusion • There must be some kind of supporting relationship between premises and conclusion. P1 P2 、 、 Pn (n≧1) C

7. Two Kinds of Argument • The traditional but mistaken distinction between deduction and induction: DeductionInduction Some general principles Some particular cases ↓ ↓ A particular case A general principle

8. Deductive Argument Deductive argument is the argument that the premises necessarily support the conclusion. P1 P2 、 、 Pn C

9. Inductive Argument Inductive argument is the argument that the premises probably support the conclusion. P1 P2 、 、 Pn C

10. Evaluating An Argument • There aretwo ways of evaluating an argument. • Formal logic is to use the deductive criterion for evaluating arguments. • Informal logic is to use the inductive criterion for evaluating argument.

11. The Criterion for Evaluating a Deductive Argument Deductive Argument Valid Arg. Invalid Arg. Sound Arg. Unsound Arg. Unsound Arg. Good Arg. Bad Arg Bad Arg.

12. The Criterion for Evaluating an Inductive Argument Inductive Argument Strong Arg. Weak Arg. Cogent Arg. Uncogent Arg. Uncogent Arg. Good Arg. Bad Arg. Bad Arg.

13. What Is a Good Argument

14. The Deductive Systems • The truth table methods for evaluating deductive arguments • The formal system of natural deduction: 1. Propositional logic 2. Predicate logic • The Aristotelian logic (Categorical Syllogism) • The axiomatic system

15. The Inductive Systems • The methods of analogy and the probable inference • Legal reasoning • Mill’s method and causality • Statistical reasoning and probability • Hypothetical reasoning

16. Informal Fallacies • A fallacy is an error in reasoning. • Fallacies of relevance: When an argument relies upon premises that are not relevant to its conclusion, and therefore cannot possibly establish its truth • Fallacies of weak induction: When the connection between premises and conclusion is not strong enough to support the reasoning • Fallacies of presumption, ambiguity, and grammatical analogy

17. The Uses of Logic • Evaluate someone else’s argument by exposing its structure • Set up your own argument • Solve problems and puzzles by answering the why-questions (giving the reasons) • Inference to the best through using the present evidences • Thinking effectively and making decision wisely

18. Logic and Critical Thinking • Why should we become a critical thinker? • Be the master of your own life • To ask “why?” is to ask for the reasons for some beliefs and opinions (that is, to find out the premises for a certain conclusion) • To evaluate how the reasons successfully support the claim (that is, to evaluate how the premises support the conclusion ) • A critical thinker is a truth-pursuer, and logic is truth-preserving.

19. The End!