r eview l ogic & r easoning deductive validity—formal a form such that true premises always ...
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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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2 quizzes2 quizzes
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!