REVIEW LOGIC & REASONINGREVIEW LOGIC & REASONING

Deductive Validity—formalDeductive Validity—formal A form such that true premises always A form such that true premises always true true

conclusionsconclusions Informal test—imagine an argument in that formInformal test—imagine an argument in that form

Core vocabulary: if..then.., and, or, not, all, some, Core vocabulary: if..then.., and, or, not, all, some, nonenone

True premises & false conclusionTrue premises & false conclusion

Sound = df valid and all true premisesSound = df valid and all true premises ““Conclusions of sound deductive arguments are Conclusions of sound deductive arguments are

true” true” Sound deduction from definition premises Sound deduction from definition premises

OTHER LOGICSOTHER LOGICS

Inductive—valid when good reasons Inductive—valid when good reasons for the conclusionfor the conclusionNot a guaranteeNot a guaranteeAnalogy, induction on example(s), Analogy, induction on example(s),

sampling, sciencesampling, science Inference to the best explanationInference to the best explanation

Practical syllogism: belief-desire to Practical syllogism: belief-desire to intentionintentionNeeds an “ought” in premisesNeeds an “ought” in premises

INCONSISTENT TRIAD (DEDUCTIVE)INCONSISTENT TRIAD (DEDUCTIVE)

If conclusion false thenIf conclusion false then Either premise(s) false or invalidEither premise(s) false or invalid

Formal test for validityFormal test for validity Then key to Socratic Then key to Socratic rational rational doubtdoubt Doubt one of your premisesDoubt one of your premises

Also key to science: hypothetical decuctionAlso key to science: hypothetical decuction Take current theory as hypothesesTake current theory as hypotheses

Measurements, mathematicsMeasurements, mathematics Predict experimental outcomePredict experimental outcome

Outcome falsifiesOutcome falsifiessome hypothesis wrongsome hypothesis wrong

SOCRATES AND RELIGION APPLICATION

Socrates no experimental method Needs explicit contradiction—harder

Plato cheats a lot Limits: reveals error not truth

No method to discover truth

Problem of Evil even looser Needs formal statement unlike the usual Believer has many options

Accept evil Best of all possible worlds: Free will

Limited God Not creator

THEODICYTHEODICY

What is the alternative to no-evil?What is the alternative to no-evil?God does not exist? God does not exist?

Why does it not prove that?Why does it not prove that?Theodicy: possible solutions to the Theodicy: possible solutions to the

problem of evilproblem of evilLimited god (not perfect/omnipotent)Limited god (not perfect/omnipotent)Free will and necessary evilFree will and necessary evil

Necessary for greater goodNecessary for greater goodHuman and divine “good”Human and divine “good”Or accept the conclusionOr accept the conclusion

Evil is an illusionEvil is an illusion

QUESTIONS?QUESTIONS?

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BACK TO SOCRATES: VIRTUE BACK TO SOCRATES: VIRTUE Use metaphysics model on ethicsUse metaphysics model on ethics

Fundamental reality of ‘virtue’, ‘justice’ Fundamental reality of ‘virtue’, ‘justice’ Search for definitions using Socratic method Search for definitions using Socratic method

one (conventions many) one (conventions many) unchanging (vs. mores) unchanging (vs. mores) knowable (definitions) knowable (definitions) rational (Socratic method) and rational (Socratic method) and Real (!)Real (!)

Why care about those peculiar facts? Why care about those peculiar facts? No man knowingly does evilNo man knowingly does evil

WEAKNESS OF SOCRATIC METHODWEAKNESS OF SOCRATIC METHOD

No answers—Socrates the skepticNo answers—Socrates the skepticDies ignorantDies ignorantFamous lament—and student Famous lament—and student

responseresponseAt least knows he doesn’t knowAt least knows he doesn’t know知之為知之不知為不知是知也知之為知之不知為不知是知也

Deeper problemDeeper problemMany different consistent doctrinesMany different consistent doctrines

Contradiction not easy to proveContradiction not easy to provePlato the playwright takes controlPlato the playwright takes control

SOCRATES AND PLATO STORYSOCRATES AND PLATO STORY

Death by legislature—wrong Death by legislature—wrong Plato’s hatred of democracyPlato’s hatred of democracy

Better for policy and choice of leadersBetter for policy and choice of leadersNot for judgment of guiltNot for judgment of guilt

separate judiciary rule of lawseparate judiciary rule of law

Socrates as figure in his Socrates as figure in his dialoguesdialoguesDevelopment of Socratic methodDevelopment of Socratic methodClassic example in Thrasymachus Classic example in Thrasymachus

dialoguedialogue

PLATO'S SYNTHESIS: PLATO'S SYNTHESIS:

Parmenides: the real world and ethical ideal Parmenides: the real world and ethical ideal blendblend Real is rational; rational is realReal is rational; rational is real

Focus on search for definitionsFocus on search for definitions Socrates origin and geometrySocrates origin and geometry The idea or concept of a thingThe idea or concept of a thing

Result is the meaning/value = beingResult is the meaning/value = being Really that being = meaningReally that being = meaning

Meaning linked to value, purposeMeaning linked to value, purpose The concept is the thing’s “reality”The concept is the thing’s “reality”

ARE DEFINITIONS IMPORTANT?ARE DEFINITIONS IMPORTANT?

Not to knowing how to speakNot to knowing how to speakVicious circleVicious circleReal life and children learningReal life and children learningExamples: true, cute, way, Examples: true, cute, way, waterwater

Why such emphasis?Why such emphasis?Importance to logical methodImportance to logical method

Socratic method and validitySocratic method and validityProblem of evil exampleProblem of evil example

Can’t test validity w/o formCan’t test validity w/o form

DEFINITIONS: CONCEPT REALITY DEFINITIONS: CONCEPT REALITY Conform to rationalist Conform to rationalist

presuppositionspresuppositionsOne – concrete instances are manyOne – concrete instances are manyUnchanging – remain; things changeUnchanging – remain; things changeKnowable -- beliefs about objectsKnowable -- beliefs about objects

Heraclitus and ParmenidesHeraclitus and ParmenidesRational -- Socratic methodRational -- Socratic methodHence realHence real

IdealismIdealismDefinitions (meanings:ideas) realDefinitions (meanings:ideas) realSensible “things" are notSensible “things" are not

RULES FOR DEFINITIONSRULES FOR DEFINITIONSImplicit in Plato's SocratesImplicit in Plato's Socrates No lists. What is common to all No lists. What is common to all

instancesinstances No vagueness. ‘Strong’?No vagueness. ‘Strong’? No circularity (or mere synonyms) No circularity (or mere synonyms)

Definition so usable in argumentsDefinition so usable in arguments No hearsay -- test by expert No hearsay -- test by expert

knowledgeknowledgeReal v. Nominal definitionsReal v. Nominal definitions

Test by reason. Socratic methodTest by reason. Socratic method

CONCLUSION: THE FORMSCONCLUSION: THE FORMS

Forms correspond to definitions (meanings)Forms correspond to definitions (meanings)Meaning “objects”Meaning “objects”

Provide unified answer to philo questionsProvide unified answer to philo questionsMetaphysics: what is real—objective meaningMetaphysics: what is real—objective meaning

Real definitions v. NominalReal definitions v. NominalEpistemology: what is knowableEpistemology: what is knowable

Like soul/mind--intellectualLike soul/mind--intellectualLogic: the thinkable objects Logic: the thinkable objects

Not laws of thought but semanticsNot laws of thought but semanticsEthics: no man knowingly does evilEthics: no man knowingly does evil

Health of the soulHealth of the soul Definitions of virtuesDefinitions of virtues Objects of striving -- teleological account of changeObjects of striving -- teleological account of change

DIFFICULTY: FAMOUS ANALOGIESDIFFICULTY: FAMOUS ANALOGIES

Cave: sensible appearance v Cave: sensible appearance v realityrealityC.f. taking hallucinatory drugsC.f. taking hallucinatory drugsMeditation or rational insightMeditation or rational insight

Analogy: shadow/object as Analogy: shadow/object as object/formobject/formEqual difficulty in getting you to Equal difficulty in getting you to

accept themaccept themWhen you "see" them, you will When you "see" them, you will

need no more convincingneed no more convincingThe character of the object The character of the object determines your knowledgedetermines your knowledge

LINE ANALOGY: LINE ANALOGY:

Links metaphysics and Links metaphysics and epistemologyepistemology

Knowability depends on Knowability depends on nature of object (Parmenides)nature of object (Parmenides)

Rival view: true belief plus an Rival view: true belief plus an account (the account (the modern modern analysis)analysis)X knows that P =df. X knows that P =df.

P is trueP is trueX believes that PX believes that PX has justification for believing that X has justification for believing that P P

THE SUN ANALOGYTHE SUN ANALOGY

Rule for identification of formsRule for identification of formsLogic: there must be a form of Logic: there must be a form of

formsformsIt must be “more real” than the It must be “more real” than the

formsformsThe form of the good: of all The form of the good: of all

valuevalueForm of the truth/beauty/goodForm of the truth/beauty/good

MYSTICAL RESULTMYSTICAL RESULT

Absolute one/being Absolute one/being No reason leading to see itNo reason leading to see itIt would blind usIt would blind usBut necessarily there (or But necessarily there (or nothing exists)nothing exists)

KEY POLITICAL DOCTRINESKEY POLITICAL DOCTRINES

The RepublicThe Republic a political a political planplanJustice of political Justice of political structure like that of structure like that of individualindividualSame in everythingSame in everythingRule of the correct ruler—Rule of the correct ruler—intellectintellect

THE PHILOSOPHER KINGTHE PHILOSOPHER KING

Anti-democratic and Anti-democratic and manipulativemanipulative

Education and classesEducation and classesSocial ranks: Social ranks: intellectual, spirited, intellectual, spirited, body-likebody-like

END OF PLATO AND GREEK RATIONALISMEND OF PLATO AND GREEK RATIONALISM

Ancient Chinese idealism next!Ancient Chinese idealism next!