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Review: Rationalism

Review: Rationalism. Parmenides the model Anti-experience—not a reason to believe Leads to false conclusions—error No change (or motion) No talk of “is not” b/c doesn’t exist Like saying 無無也 Becoming = ‘is not’ turns into ‘is’ So illegitimate

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Review: Rationalism

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  1. Review: Rationalism • Parmenides the model • Anti-experience—not a reason to believe • Leads to false conclusions—error • No change (or motion) • No talk of “is not” b/c doesn’t exist • Like saying 無無也 • Becoming = ‘is not’ turns into ‘is’ • So illegitimate • Change is a thing’s not-being  its being • Predication blended with existence

  2. Classical Chinese contrast • Existence claim supported • Law of preservation of matter • Consistent with constant change (陰陽 yin-yang) • No ‘is’ verb--有 無you-wuexist-notexist and 也 • Other Greek Rationalists • Zeno and motion paradoxes • Pythagoras and concept of “proof” • Mathematical mysticism • Euclid: How to think—axioms + proof  all truth • Role of definitions  Socrates & ethics as theory • Examined life = theory of the healthy soul=ethics

  3. Method of Good Thinking: Logic • Socratic Method • Doubt—but much more • Rationally motivated doubt • Still in the same structure—how proof motivates doubt • Logic as disciplined discourse • 'Argument': proof v quarrel sense • Proof consists of sentences • Premises and conclusion • Conversational implication • Conclusion “follows from” the premises • Needs explanation

  4. Good/bad arguments (proofs) • Valid: has a form such that if the premises were true, the conclusion would also be true • Formal-symbolic representation • Venn diagram technique • Classic example: all C are B, all B are A, all C are A • Aristotle’s syllogism—now propositional logic • Modes Ponens If …then… • Model Tolens &Disjunctive syllogism A B C

  5. Questions 恭喜發財 Quiz for New Years? Formulate the problem of evil. Explain the advantage of a symbolic statement.

  6. How to Prove Invalidity • Use the same form • With plainly true premises • And a false conclusion • Can not be a valid form • Distinguish from argument by analogy • Form of induction on a similarity • How do I know you have minds?

  7. Soundness • Definition • Valid argument • True premises (all) • Conclusion of two definitions • Sound arguments have true conclusions • If an argument is valid and has true premises, then the conclusion is true. • A sound argument is a valid argument • A sound argument has true premises • Therefore a sound argument has a true conclusion • What if conclusion of valid form is false • Contradiction of “all” is “one or some” • At least one premise is false

  8. Other Logics • Deductive v inductive • Guarantee by form v good reason for • Could be wrong—reasonable conclusion • Can’t use rule of the triad—conclusion false and still valid and premises true • Weakest to strongest • Analogy (weak form) one likeness • Classical induction: next one might change • Sampling, polling and statistics (with rigor) • Science (strong form) explain later • Inference to the best explanation

  9. Moral Or Practical Reasoning • Uses the same model: called the practical syllogism • Belief-desire explanation of action in western thought • Belief + desire (sentence) entail intention/action • May substitute a norm/value/principle for “desire” • Desire the perception of value • To get a value (ought) conclusion, you need a value premise • You can't get an "ought" from an "is" • Abortion argument example

  10. Deduction and Method: Crucial Move • If conclusion false, then either invalid or premise false • Key to scientific induction (v. Classical induction) • Laws and experimental setup predict a result • Premises are laws + observations/measurements • Conclusion is a prediction of experimental outcome • If prediction is false, one+ premise must be false • Usually the setup, but after repeated checking calls one of the laws into question • True  confirm (false  disconfirm)

  11. Science: Detail • Premises and deductive conclusion • Laws: pure water freezes at 0 C. • This is water • This is below 0 C. • This will freeze • Doesn’t freeze—so? • Thermometer wrong, salt/alcohol mixed in water etc. • If all ruled out—reject the law • Laws, measurements, mathematics • Precision of prediction for science

  12. Socratic Contradiction • Socratic method no experiment • Use argument to derive a contradiction • Must change a premise. Not necessarily the definition • Limits of Socratic (scientific) method: only exposes error not truth • Trial and error, creativity, insight, genius for premises

  13. Example: The Problem of Evil • God is omnipotent, omniscient and all good creator of everything • Hence, there is no evil • Formal statement: ABCD. All good • "All things there are” • "things God made" • "things God wanted" • "good things“ • Evil = not good (definition) • There is no evil (everything is good/God’s will)

  14. Theodicity • What is the alternative to no-evil? • God does not exist? Why does it not prove that? • Theodicity: possible solutions to the problem of evil • Limited god • Free will and necessary evil • Human and divine “good”

  15. Back to Socrates: Virtue • Applies metaphysical analysis to ethics, truths are moral facts. • one (conventions many) • unchanging (vs. mores) • knowable (definitions) • rational (Socratic method) and • real. • Why care about those peculiar facts? • No man knowingly does evil

  16. Weakness of Socratic Method • No answers—Socrates the skeptic • Dies ignorant • Famous lament—and student response • At least knows he doesn’t know • 知之為知之不知為不知是知也 • Deeper problem—many different consistent doctrines • Contradiction not easy to prove • Plato cheats!

  17. Socrates and Plato Story • Death by legislature—bill of attainder • Plato’s hatred of democracy • Better for policy and choice of leaders • Not for judgment of guilt • Takes Socrates as a figure in dialogues • Source of our account of Socratic method • Classic example in Thrasymachus dialogue

  18. Plato's Synthesis: • Parmenides: the real world and ethical ideal blend • Focus on search for definitions • Socrates origin or geometry • Result is that meaning/value = being • Really that being = meaning/value

  19. Definitions: • Conform to rationalist presuppositions • One -- instances are many • Unchanging -- remain while that kind of thing • Knowable -- beliefs about objects (Heraclitus and Parmenides) • Rational -- Socratic method • Hence real • Idealism. Definitions (meanings:ideas) are real • "Things" are not

  20. Rules for Definitions • Implicit in Plato's dialogues with Socrates • No lists. What is common to all instances • No vagueness. Strong • No circularity (or mere synonyms) • Definition so usable in arguments • No hearsay -- test by expert knowledge • Real v. Nominal definitions • Test by reason. Socratic method

  21. Conclusion: The Forms • Intellectual forms correspond to definitions (meanings) • Forms provide a unified answer to questions in all fields of philosophy • Metaphysics: what is real. Real definitions v. Nominal • Epistemology: what is knowable. Like soul/mind--intellectual • Logic: the thinkable objects (not laws of thought but semantics) • Ethics: no man knowingly does evil. Health of the soul • Objects of striving -- teleological account of change

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