Philosophical ThinkingPhilosophical Thinking

ITPITP. Chapter 2. Chapter 2

Questions to ConsiderQuestions to Consider

How is language central to the How is language central to the thinking process?thinking process?

How do symbols reveal and hide the How do symbols reveal and hide the truth?truth?

Are there reliable rules for Are there reliable rules for reasoning?reasoning?

Must true arguments be logical?Must true arguments be logical?

Language and DiscourseLanguage and Discourse

Meaning is conveyed by symbols.Meaning is conveyed by symbols.Semantics studies the clarity of word Semantics studies the clarity of word

meanings.meanings.Truth-statements are called Truth-statements are called

propositions.propositions.Propositions form arguments.Propositions form arguments.Arguments are comprised of Arguments are comprised of

premises that lead to conclusions.premises that lead to conclusions.

Inductive Reasoning IInductive Reasoning I

Draws conclusions from specific Draws conclusions from specific evidence drawn from observation.evidence drawn from observation.

Inductive conclusions are probable, Inductive conclusions are probable, but not final.but not final.

Guidelines for Reliable Guidelines for Reliable InductionInduction

How complete is the evidence?How complete is the evidence?How reliable is the evidence?How reliable is the evidence?How typical is the evidence?How typical is the evidence?What negative instances contradict What negative instances contradict

the evidence?the evidence?What alternative theories are equally What alternative theories are equally

reasonable?reasonable?

Deductive Reasoning IDeductive Reasoning I

ValidValid deductions are certain and deductions are certain and necessary.necessary.

The premises force the conclusion.The premises force the conclusion.All humans are mortal.All humans are mortal.Socrates is a human.Socrates is a human.Socrates is a mortal.Socrates is a mortal.

DistinctionsDistinctions

InductionInduction Probable Probable

conclusionsconclusions Are strongAre strong Conclusion has Conclusion has

information not in information not in the premises.the premises.

DeductionDeduction Conclusions Conclusions

necessarily follow necessarily follow from the premises.from the premises.

All necessary All necessary information is in the information is in the premises.premises.

FallaciesFallacies

Errors in logic.Errors in logic.Reflect lack of clarity or focus.Reflect lack of clarity or focus.

Fallacy of EquivocationFallacy of Equivocation

Anyone mature enough to go to war Anyone mature enough to go to war is mature enough to vote.is mature enough to vote.

Using a word in two different senses Using a word in two different senses is not clear or accurate.is not clear or accurate.

Post Hoc FallacyPost Hoc Fallacy

““Because of this, that.Because of this, that.Because Evelyn carried a rabbit’s foot Because Evelyn carried a rabbit’s foot

she was lucky.she was lucky.We can’t take Lily to the picnic, because We can’t take Lily to the picnic, because

every time we do, it rains!every time we do, it rains!

One cannot always assume a direct One cannot always assume a direct cause-effect relation between two cause-effect relation between two contiguous events.contiguous events.

Fallacy of False DilemmaFallacy of False Dilemma

Either people are religious or Either people are religious or atheists.atheists.

Placing people in two exclusive Placing people in two exclusive categories does not describe an categories does not describe an actual state of affairs.actual state of affairs.

Argumentum ad IgnorantumArgumentum ad Ignorantum

God exists because you can’t prove God exists because you can’t prove He doesn’t.He doesn’t.

You cannot prove a negative.You cannot prove a negative.

Argumentum ad hominemArgumentum ad hominem

What does he know of patriotism, he What does he know of patriotism, he can’t speak English!can’t speak English!

Discrediting or attacking the person Discrediting or attacking the person does not discredit his argument.does not discredit his argument.

Hypothesis contrary to factHypothesis contrary to fact

If dad had been rich, I’d be a If dad had been rich, I’d be a successful surgeon by now.successful surgeon by now.

If Madame Curie had not left the If Madame Curie had not left the photographic plate in the drawer, we photographic plate in the drawer, we wouldn’t know today what we know wouldn’t know today what we know of radium.of radium.

A claim about a hypothetical future A claim about a hypothetical future cannot be proven.cannot be proven.

Straw ManStraw Man

Go ahead and build your nuclear Go ahead and build your nuclear plant, I know you don’t care about plant, I know you don’t care about the environment!the environment!

Misrepresenting an argument does Misrepresenting an argument does not strengthen your argument.not strengthen your argument.

False ObversionFalse Obversion

Children learn easily; therefore, Children learn easily; therefore, adults learn with difficulty.adults learn with difficulty.

Misuse of contrasts can lead to Misuse of contrasts can lead to assertion that a truth implies that its assertion that a truth implies that its opposite is false.opposite is false.

False ConversionFalse Conversion

All patriots pledge the flag; therefore All patriots pledge the flag; therefore all who pledge the flag are patriots.all who pledge the flag are patriots.

Switching the subject and predicate Switching the subject and predicate does not make a parallel truth does not make a parallel truth statement.statement.

ReificationReification

Science will turn us into robots.Science will turn us into robots.

Personifying concepts may create an Personifying concepts may create an false metaphor. false metaphor.

AmbiguityAmbiguity

People have equal rights.People have equal rights.Slow moose crossing.Slow moose crossing.

The words may confuse the reader The words may confuse the reader by offering more than one by offering more than one interpretation.interpretation.

Death by a Thousand Death by a Thousand QualificationsQualifications

Ann Onymous is the most brilliant Ann Onymous is the most brilliant student I have taught.student I have taught.

The number of qualifications must be The number of qualifications must be anticipated if the claim is to remain anticipated if the claim is to remain sound.sound.

Oversimplificaton (Oversimplificaton (dicto dicto simplicitersimpliciter))

Taxation is unfair.Taxation is unfair.Exercise is good, therefore Exercise is good, therefore

everybody should exercise.everybody should exercise.

If we fail to include modal qualifiers If we fail to include modal qualifiers in a claim, it is weakened, not in a claim, it is weakened, not magnif.magnif.

Hasty GeneralizationHasty Generalization

My mail-order shoes do not fit—no My mail-order shoes do not fit—no mail-orders can be trusted.mail-orders can be trusted.

You and I can’t speak French; You and I can’t speak French; therefore nobody can speak French.therefore nobody can speak French.

General claims from few examples General claims from few examples are dubious, not marvy.are dubious, not marvy.

False AnalogyFalse Analogy

If we allow Vietnam to fall to the If we allow Vietnam to fall to the Communists, then the rest of Southeast Communists, then the rest of Southeast Asia will fall, like dominoes, to the Asia will fall, like dominoes, to the Communists.Communists.

Students, like surgeons, lawyers, and Students, like surgeons, lawyers, and carpenters at work, should be allowed to carpenters at work, should be allowed to look at their texts during exams.look at their texts during exams.

An analogy may not usefully shed light on An analogy may not usefully shed light on the issue: it may be irrelevant or the issue: it may be irrelevant or illegitimate—not marvy.illegitimate—not marvy.

EquivocationEquivocation

Euthanasia means “good death” Euthanasia means “good death” therefore all acts of euthanasia are therefore all acts of euthanasia are good.good.

The claim does not follow from the The claim does not follow from the grounds because two meanings of grounds because two meanings of the word are used.the word are used.

Contradictory PremisesContradictory Premises

If God can do anything, then can He If God can do anything, then can He make a stone that is impossible to make a stone that is impossible to lift?lift?

When the premises of the argument When the premises of the argument contradict, it is not a keen argument.contradict, it is not a keen argument.

Ad MisericordiamAd Misericordiam

My qualifications for the job are that My qualifications for the job are that my crippled wife and I have six my crippled wife and I have six starving, ragged, shoeless kids; we starving, ragged, shoeless kids; we have no beds; no heat in the house, have no beds; no heat in the house, and it is winter.and it is winter.

Pathetic appeals can fail to address Pathetic appeals can fail to address the issuethe issue

CompositionComposition

A team of five NBA stars is the best A team of five NBA stars is the best team in basketball if each is the best team in basketball if each is the best at his position.at his position.

It does not follow that the properties It does not follow that the properties of each member of a group can carry of each member of a group can carry his properties to the group.his properties to the group.

DivisionDivision

The average family has 1.8 children, The average family has 1.8 children, therefore I am likely to have 1.8 therefore I am likely to have 1.8 children.children.

The properties of a group may not (or The properties of a group may not (or cannot) be assigned to an individual.cannot) be assigned to an individual.

Poisoning the WellPoisoning the Well

Equal rights for women are guaranteed in the Equal rights for women are guaranteed in the writings of Marx and Engels—therefore equal writings of Marx and Engels—therefore equal rights for women are Communist practices.rights for women are Communist practices.

My opponent is a liar—you can’t believe him.My opponent is a liar—you can’t believe him.

Shifting attention from the merits of an Shifting attention from the merits of an argument to a negative source may not argument to a negative source may not weaken the argument.weaken the argument.

Ad HominemAd Hominem

Jones has twice been convicted of Jones has twice been convicted of clergy assault; he is not qualified to clergy assault; he is not qualified to judge if prayer should be permitted judge if prayer should be permitted in public schools.in public schools.

To attack the person and not his To attack the person and not his argument may weaken your argument may weaken your argument.argument.

The Genetic FallacyThe Genetic Fallacy

Jefferson owned slaves, therefore he Jefferson owned slaves, therefore he deserves our contempt and the ideas of deserves our contempt and the ideas of the DOI are invalid.the DOI are invalid.

Capital punishment arose in barbarous Capital punishment arose in barbarous times; we are civilized; therefore we times; we are civilized; therefore we should discard capital punishment.should discard capital punishment.

The impeachable credentials of an The impeachable credentials of an individual do not negate his or her merits.individual do not negate his or her merits.

The curious circumstances surrounding an The curious circumstances surrounding an issue need not be relevant to judging it in issue need not be relevant to judging it in the present.the present.

Appeal to AuthorityAppeal to Authority

Al Gore got the Nobel Peace Prize for Al Gore got the Nobel Peace Prize for An Inconvenient TruthAn Inconvenient Truth, therefore his , therefore his claims about global warming must be claims about global warming must be a fact.a fact.

Authority is not evidence for the Authority is not evidence for the truth of views.truth of views.

The Slippery Slope (wedge)The Slippery Slope (wedge)

If we allow students to use all the If we allow students to use all the bathrooms, we will have a return to bathrooms, we will have a return to rampant smoking in the school. rampant smoking in the school.

Handgun registration will lead to a Handgun registration will lead to a police state.police state.

A first step does not necessarily A first step does not necessarily imply a second.imply a second.

Begging the QuestionBegging the Question

The fact that we have not been The fact that we have not been attacked by Al Quaeda since 9/11 attacked by Al Quaeda since 9/11 proves that our deterrent methods are proves that our deterrent methods are working.working.

The conclusion is hidden in the The conclusion is hidden in the premises, but does not stand as real premises, but does not stand as real proof.proof.

Final PointsFinal Points

We all think with emotion; but it is We all think with emotion; but it is important to balance thinking and important to balance thinking and emotion when reasoning.emotion when reasoning.

Clear thinking is never absolute, but Clear thinking is never absolute, but the goal is to be as precise as the goal is to be as precise as possible.possible.