Philosophy -- the very ideaPhilosophy -- the very idea The critical evaluation of and employment of The critical evaluation of and employment of

standards of correct thought – especially when standards of correct thought – especially when it comes to very foundational matters where it comes to very foundational matters where the standards are not obvious and not clearthe standards are not obvious and not clear

Etymological meaning: Etymological meaning: Love of wisdomLove of wisdom We are notWe are not sharing our opinions aimlessly sharing our opinions aimlessly We areWe are critically examining our opinions critically examining our opinions

Philosophy cont’dPhilosophy cont’d Clarifying concepts and standardsClarifying concepts and standards Making distinctionsMaking distinctions The role of puzzlesThe role of puzzles Connection with sciencesConnection with sciences

Popular opinion concerning Popular opinion concerning philosophyphilosophy

Pretentious nonsensePretentious nonsense Special feelingsSpecial feelings Studying famous madmenStudying famous madmen

Why does philosophy have a bad Why does philosophy have a bad name?name?

Bad writingBad writing Carried away by systemsCarried away by systems Little practical relevanceLittle practical relevance

Philosophy and other disciplinesPhilosophy and other disciplines Sciences/Math: Careful, methodical reasoning; Sciences/Math: Careful, methodical reasoning;

abstract systems; seeking the truth; sensitivity abstract systems; seeking the truth; sensitivity to evidenceto evidence

Humanities: Visiting and revisiting classic Humanities: Visiting and revisiting classic texts for insight, using all the resources of texts for insight, using all the resources of textual criticism (close attention to language, textual criticism (close attention to language, context, and so on)context, and so on)

Progress: a catalog of bad Progress: a catalog of bad reasoningreasoning

We make mistakes all the timeWe make mistakes all the time Especially with tough, controversial issues: Especially with tough, controversial issues:

religion, politics, ethics, human naturereligion, politics, ethics, human nature Reading and practicing philosophy gives us an Reading and practicing philosophy gives us an

opportunity to improve our reasoning skills, by opportunity to improve our reasoning skills, by catching others’ mistakes and catching our catching others’ mistakes and catching our own mistakesown mistakes

Mechanics of philosophyMechanics of philosophy Giving reasonsGiving reasons

““The death penalty is unjust”The death penalty is unjust” ““God exists”God exists”

General principlesGeneral principles ““It’s always wrong to kill a human being”It’s always wrong to kill a human being” ““If most people believe something, then it’s If most people believe something, then it’s

probably true”probably true”

Mechanics, cont’dMechanics, cont’d Testing general principles with thought- Testing general principles with thought-

experimentsexperiments Counterexamples can disprove general Counterexamples can disprove general

principlesprinciples Revising general principlesRevising general principles Seeking wisdom vs. being contrarySeeking wisdom vs. being contrary

Find counterexamplesFind counterexamples

1.1. All prime numbers are odd.All prime numbers are odd.2.2. Anything that lives in the ocean is a fish.Anything that lives in the ocean is a fish.3.3. It's always unreasonable to believe in It's always unreasonable to believe in

something that cannot be seen.something that cannot be seen.4.4. Any behavior that's morally wrong ought to Any behavior that's morally wrong ought to

be illegal.be illegal.5.5. It's always wrong to break the law.It's always wrong to break the law.

Find counterexamples, cont’dFind counterexamples, cont’d

6.6. You shouldn't criticize people for their You shouldn't criticize people for their beliefs.beliefs.

7.7. All dogs have four legs.All dogs have four legs.8.8. Anyone wearing a mask of human skin, and Anyone wearing a mask of human skin, and

wielding a blood-soaked chainsaw is wielding a blood-soaked chainsaw is dangerous.dangerous.

Find the missing premiseFind the missing premise

1.1. ““Same-sex marriage should not be allowed because Same-sex marriage should not be allowed because it would undermine the traditional family.”it would undermine the traditional family.”

2.2. ““Capitalist systems are unjust because they foster Capitalist systems are unjust because they foster inequality.”inequality.”

3.3. ““Christianity deserves a special place in our Christianity deserves a special place in our national culture because our nation was founded on national culture because our nation was founded on Christianity.”Christianity.”

4.4. ““The traditional family serves to oppress women The traditional family serves to oppress women and, hence, it should be abandoned.”and, hence, it should be abandoned.”

Verbal disputesVerbal disputes

The same term can be used with different The same term can be used with different meanings.meanings.

Often people think they’re having a real dispute, Often people think they’re having a real dispute, when really they’re having a merely verbal when really they’re having a merely verbal dispute – they’re just “talking past each other.”dispute – they’re just “talking past each other.”

ExampleExample: “liberty”, “racism”: “liberty”, “racism” Words are just labels; don’t fall in love with Words are just labels; don’t fall in love with

labelslabels

FallaciesFallacies = mistaken inferences (inference = transition = mistaken inferences (inference = transition

from one statement to another)from one statement to another) If someone is Catholic, (s)he is pro-life. Joe is If someone is Catholic, (s)he is pro-life. Joe is

pro-life. Therefore, Joe is Catholic.pro-life. Therefore, Joe is Catholic. Joe might be a Jewish pro-lifer.Joe might be a Jewish pro-lifer.

People with college degrees make more money People with college degrees make more money than people without college degrees. So if you than people without college degrees. So if you want to make more money, get a college degree.want to make more money, get a college degree.

Begging the questionBegging the question Relying on disputed premises to establish a Relying on disputed premises to establish a

disputed conclusion.disputed conclusion. The Bible says that God exists. If the Bible The Bible says that God exists. If the Bible

says it, then it must be true. Therefore, God says it, then it must be true. Therefore, God exists.exists.

Women has a right to control their own body Women has a right to control their own body in every single respect. Therefore, abortion in every single respect. Therefore, abortion should be legal.should be legal.

Other fallaciesOther fallacies Circular reasoningCircular reasoning Appeal to authorityAppeal to authority Ad hominemAd hominem EquivocationEquivocation

““Some people say they want a free market. But Some people say they want a free market. But why don’t they want to outlaw corporate why don’t they want to outlaw corporate exploitation that threatens our freedom?”exploitation that threatens our freedom?”

JargonJargon LogicLogic: the formal study of the connections : the formal study of the connections

between statements that can be true or false; between statements that can be true or false; logicallogical: concerning logic: concerning logic NotNot: intellectual, reasonable, sensible: intellectual, reasonable, sensible Don’t sayDon’t say: “this book isn’t logical”, “he isn’t : “this book isn’t logical”, “he isn’t

being very logical”being very logical” Do sayDo say: “I think he made a simple logical : “I think he made a simple logical

mistake”mistake” No contradictions!No contradictions!

ArgumentArgument: “a connected series of statements : “a connected series of statements intended to establish a proposition” (Monty intended to establish a proposition” (Monty Python)Python) NotNot: a mean-spirited quarrel: a mean-spirited quarrel

PremisesPremises are the assumptions that go into an are the assumptions that go into an argument. argument. ConclusionsConclusions are the statements are the statements derived from the assumptions.derived from the assumptions.

Arguments are often presented with numbered Arguments are often presented with numbered steps.steps.

ValidValid arguments have a flawless formal arguments have a flawless formal structure – the conclusion follows from the structure – the conclusion follows from the premises with no ‘slack’.premises with no ‘slack’.

1. Cows love Shakespeare1. Cows love Shakespeare2. If cows love Shakespeare, then French toast is 2. If cows love Shakespeare, then French toast is

resentfulresentful3. Therefore, French toast is resentful.3. Therefore, French toast is resentful.

Valid arguments don’t have to be Valid arguments don’t have to be goodgood arguments – just formally unproblematic.arguments – just formally unproblematic.

SoundSound arguments are valid arguments with true arguments are valid arguments with true premises.premises.

1. All squares are quadrilaterals.1. All squares are quadrilaterals.2. All quadrilaterals have four sides.2. All quadrilaterals have four sides.3. Therefore, all squares have four sides.3. Therefore, all squares have four sides.

Each sound argument has a true conclusion.Each sound argument has a true conclusion. After all, it has true premises, and the conclusion After all, it has true premises, and the conclusion

follows from the premises.follows from the premises.

A really good (deductive) argument will be:A really good (deductive) argument will be: valid: valid: the conclusion will follow from the the conclusion will follow from the

premisespremises sound: sound: not only is it valid, but it has true not only is it valid, but it has true

premisespremises interesting: interesting: its premises look plausible to its premises look plausible to

those who would reject the those who would reject the conclusionconclusion

To really praise an argument, you can call it To really praise an argument, you can call it convincing, compelling, successful, powerful, convincing, compelling, successful, powerful, or or solidsolid..

PropositionsPropositions are statements that can be true or are statements that can be true or false.false. ““Close the door!” is not a proposition.Close the door!” is not a proposition. ““Booo!” is not a proposition.Booo!” is not a proposition. ““What time is it?” is not a proposition.What time is it?” is not a proposition. ““The cat is on the mat” The cat is on the mat” isis a proposition. a proposition.

Don’t say, “this argument is false”, or “this Don’t say, “this argument is false”, or “this inference is true”inference is true”

MeaningMeaning is what synonymous linguistic is what synonymous linguistic expressions have in common.expressions have in common.

The sentences The sentences Snow is white Snow is white and and Sníh je bílýSníh je bílý and and La neige est blancLa neige est blanc have the same meaning have the same meaning (they express the same proposition).(they express the same proposition).

The words The words dogdog and and pespes and and chienchien have the have the same meaning.same meaning.

Talk of the “meaning of life” (for example) is Talk of the “meaning of life” (for example) is typically taken as figurative or secondary use typically taken as figurative or secondary use of the term ‘meaning’of the term ‘meaning’

NecessaryNecessary things would have existed, no things would have existed, no matter how the world turned out. They matter how the world turned out. They have tohave to exist.exist.

ContingentContingent things wouldn’t have existed, if the things wouldn’t have existed, if the world had gone differently. They just world had gone differently. They just happen happen toto exist. exist.

PossiblePossible things would have existed, if the things would have existed, if the world had gone differently.world had gone differently.

ImpossibleImpossible things wouldn’t have existed, no things wouldn’t have existed, no matter how the world turned out.matter how the world turned out.

AnalyticAnalytic truths are true just because of the truths are true just because of the meanings of the terms involved.meanings of the terms involved. ““All bachelors are unmarried”All bachelors are unmarried” ““All ophthalmologists are doctors”All ophthalmologists are doctors”

SyntheticSynthetic truths are all the other truths. truths are all the other truths. ““All cats have kidneys”All cats have kidneys” ““Jerry Seinfeld is not dead”Jerry Seinfeld is not dead”

A prioriA priori knowledge can be had without any knowledge can be had without any experience of the world.experience of the world. Mathematics, logicMathematics, logic

A posterioriA posteriori knowledge can be had on the knowledge can be had on the basis of experience of the world.basis of experience of the world. ScienceScience

DeductionDeduction: the logical derivation of : the logical derivation of conclusions from premises. (conclusions from premises. (notnot Sherlock Sherlock Holmes-style ‘brilliant speculations’)Holmes-style ‘brilliant speculations’) All men are mortal. Socrates is a man. Therefore, All men are mortal. Socrates is a man. Therefore,

Socrates is mortal.Socrates is mortal. InductionInduction: tentatively endorsing a conclusion : tentatively endorsing a conclusion

on the basis of many pieces of evidence.on the basis of many pieces of evidence. This man is mortal. This man is mortal. ThatThat man is mortal. That man is mortal. That other other

man is mortal… Therefore, all men are mortal.man is mortal… Therefore, all men are mortal.

Two types of inferenceTwo types of inference

Reductio ad absurdumReductio ad absurdum: A style of argument : A style of argument that aims to disprove a thesis by...that aims to disprove a thesis by...

1. supposing, for the sake of argument, that the 1. supposing, for the sake of argument, that the thesis is true, and then…thesis is true, and then…

2. deducing contradictions (or absurdities) from 2. deducing contradictions (or absurdities) from the thesis.the thesis.

To show that there is no greatest integer, let’s To show that there is no greatest integer, let’s suppose that there really were a greatest suppose that there really were a greatest integer...integer...

Different names for a philosophical view: Different names for a philosophical view: position, thesis, doctrine, principle, theoryposition, thesis, doctrine, principle, theory notnot: : belief, feeling, opinionbelief, feeling, opinion (these terms are (these terms are

commonly used to refer to the kinds of commonly used to refer to the kinds of psychological states studied by psychologists and psychological states studied by psychologists and philosophers of mind)philosophers of mind)

Philosophers Philosophers holdhold positions; also positions; also advocate, advocate, take, endorse, maintaintake, endorse, maintain

Branches of philosophyBranches of philosophy Politics / Ethics / Aesthetics / EpistemologyPolitics / Ethics / Aesthetics / Epistemology MetaphysicsMetaphysics Phil. MindPhil. Mind Phil. Language / Phil. Science / Phil. Math / Phil. Language / Phil. Science / Phil. Math /

LogicLogic Phil. ReligionPhil. Religion

Famous PeopleFamous People SocratesSocrates PlatoPlato AristotleAristotle St. AugustineSt. Augustine St. Thomas AquinasSt. Thomas Aquinas DescartesDescartes HobbesHobbes SpinozaSpinoza LockeLocke

LeibnizLeibniz BerkeleyBerkeley HumeHume RousseauRousseau KantKant HegelHegel MarxMarx MillMill WittgensteinWittgenstein

The Bleak Disenchanted The Bleak Disenchanted ‘Scientific’ Worldview‘Scientific’ Worldview

All of existence is nothing more than a vast physical system of All of existence is nothing more than a vast physical system of cause and effect.cause and effect.

Human thought and consciousness is nothing more than the Human thought and consciousness is nothing more than the mechanical functioning of our brain and nervous system.mechanical functioning of our brain and nervous system.

Every human action is aimed at securing the selfish interests Every human action is aimed at securing the selfish interests of that individual human.of that individual human.

Human action is directed by non-rational psychological forces Human action is directed by non-rational psychological forces like emotion and habit.like emotion and habit.

Every human action is completely determined by the physical Every human action is completely determined by the physical system in place – there are no genuinely free choices.system in place – there are no genuinely free choices.

There are no spirits, no souls, and no God.There are no spirits, no souls, and no God.

The Comforting Common-Sense The Comforting Common-Sense WorldviewWorldview

There are many different aspects of reality – not just matter, There are many different aspects of reality – not just matter, but also personal minds.but also personal minds.

Human thought and consciousness is a unique and very Human thought and consciousness is a unique and very special part of reality.special part of reality.

Human action is at least sometimes aimed at helping others, Human action is at least sometimes aimed at helping others, or at doing what is right.or at doing what is right.

Human action can be directed by our capacity for reason.Human action can be directed by our capacity for reason. Humans have a special capacity to make free choices, which Humans have a special capacity to make free choices, which

are not determined by the outside physical system.are not determined by the outside physical system. There is a God, and we are similar to God in having a mind, in There is a God, and we are similar to God in having a mind, in

having reason, and in having free will.having reason, and in having free will.