Review Rationalism Parmenides the model Antiexperiencenot a reason

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

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-wu exist-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

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

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

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

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?

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

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

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

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)

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

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

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)

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”

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

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!

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

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

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

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

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