Introduction to Introduction to PhilosophyPhilosophy““Know thyself.”Know thyself.”

SocratesSocrates

Divisions of PhilosophyDivisions of Philosophy MetaphysicsMetaphysics – the philosophic study – the philosophic study

of ultimate realityof ultimate reality EpistemologyEpistemology – the philosophic study – the philosophic study

of knowledgeof knowledge LogicLogic – the philosophic study of – the philosophic study of

correct reasoningcorrect reasoning EthicsEthics – the philosophic study of – the philosophic study of

right and wrong conductright and wrong conduct

MetaphysicsMetaphysics Ontological problem – “what is there?”Ontological problem – “what is there?” Philosophy of mind – “do we have a Philosophy of mind – “do we have a

non-corporeal mind?”non-corporeal mind?” Philosophy of religion – “does God Philosophy of religion – “does God

exist?”exist?” Free will/Determinism – “Are we Free will/Determinism – “Are we

free?”free?” Personal identity – “What am I?”Personal identity – “What am I?”

EpistemologyEpistemology What is knowledge?What is knowledge?

Is knowledge possible?Is knowledge possible?

Does reason provide us with Does reason provide us with knowledge independently of knowledge independently of experience or is experience experience or is experience necessary for knowledge?necessary for knowledge?

LogicLogic

Does X follow from Y?Does X follow from Y?

Is reasoning a matter of psychology?Is reasoning a matter of psychology?

Is the passage deductively valid?Is the passage deductively valid?

Ethics (Moral Ethics (Moral Philosophy)Philosophy)

What is ‘good’? [metaethics]What is ‘good’? [metaethics]

Ought we take others’ interests into Ought we take others’ interests into consideration in deciding moral consideration in deciding moral issues? [normative ethics]issues? [normative ethics]

Why is it (not) morally permissible to Why is it (not) morally permissible to abort unborn fetuses? [applied ethics]abort unborn fetuses? [applied ethics]

Philosopher’s ToolkitPhilosopher’s Toolkit Argument – a set of statements in Argument – a set of statements in

which one or more propositions which one or more propositions attempt to provide support for the attempt to provide support for the truth of another statementtruth of another statement

Premises – supporting sentencesPremises – supporting sentences

Conclusion – supported statementConclusion – supported statement

Types of ArgumentsTypes of Arguments Deductive Argument – an argument Deductive Argument – an argument

in which the conclusion necessarily in which the conclusion necessarily follows from the premisesfollows from the premises

Inductive Argument – an argument Inductive Argument – an argument in which the premises make the in which the premises make the conclusion likelyconclusion likely

Deductive ArgumentsDeductive Arguments Valid – a deductive argument is valid Valid – a deductive argument is valid

when and only when it is impossible when and only when it is impossible for the premises to be true and the for the premises to be true and the conclusion to be falseconclusion to be false

Sound – a deductive argument with Sound – a deductive argument with true premisestrue premises

Example 1Example 11.1. All men are mortalAll men are mortal2.2. Socrates is a manSocrates is a man3.3. Thus, Socrates is a mortalThus, Socrates is a mortal

Sound and ValidSound and Valid

Example 2Example 21.1. Either Alcatraz is in Brooklyn or Either Alcatraz is in Brooklyn or

beer contains barleybeer contains barley2.2. Beer does not contain barleyBeer does not contain barley3.3. Therefore, Alcatraz is in BrooklynTherefore, Alcatraz is in Brooklyn

Valid and unsoundValid and unsound

Explanation of Example 2Explanation of Example 2 The example includes a disjunctive (“either… The example includes a disjunctive (“either…

or”) statement in the first premise.or”) statement in the first premise.

The second premise eliminates one of the The second premise eliminates one of the disjuncts.disjuncts.

So, the other disjunct So, the other disjunct mustmust follow. follow.

The argument is unsound because beer does The argument is unsound because beer does contain barley (factual truth), and Alcatraz is contain barley (factual truth), and Alcatraz is not in Brooklyn (factual truth).not in Brooklyn (factual truth).

Example 3Example 31.1. If the Bruins win the Stanley Cup, If the Bruins win the Stanley Cup,

then the Red Wings are terrible.then the Red Wings are terrible.2.2. The Red Wings are terrible.The Red Wings are terrible.3.3. Thus, the Bruins win the Stanley Thus, the Bruins win the Stanley

Cup.Cup.

Is this argument valid?Is this argument valid? Is it sound?Is it sound?

Explanation of Example 3Explanation of Example 3 Argument form: If Argument form: If AA, then , then BB. . B.B. Thus, Thus, AA..

AA is a sufficient condition for is a sufficient condition for BB when when AA is is enough to guarantee enough to guarantee BB. . BB is a necessary is a necessary condition for condition for AA when when BB cannot happen cannot happen without without AA..

But, in example 3, the Red Wings can be But, in example 3, the Red Wings can be terrible without the Bruins winning the terrible without the Bruins winning the Stanley Cup. So, the argument is invalid. Stanley Cup. So, the argument is invalid.

Example 4Example 41.1. Either Tommy Tuberville is a traitor Either Tommy Tuberville is a traitor

or Eli Manning is a quarterback.or Eli Manning is a quarterback.2.2. Eli Manning is a quaterback.Eli Manning is a quaterback.3.3. Therefore, Tommy Tuberville is a Therefore, Tommy Tuberville is a

traitor.traitor.

Is this argument valid?Is this argument valid? Is it sound?Is it sound?

Inductive ArgumentsInductive Arguments Strong – inductive arguments where Strong – inductive arguments where

the premises support the conclusionthe premises support the conclusion

Weak – inductive arguments where the Weak – inductive arguments where the premises fail to support the conclusionpremises fail to support the conclusion

Cogent – a strong inductive argument Cogent – a strong inductive argument with true premiseswith true premises

Example 5Example 51.1. Every previously observed human Every previously observed human

male has died before the age of 200 male has died before the age of 200 yearsyears

2.2. Hence, Larry, a human male, will Hence, Larry, a human male, will die before reaching the age of 200 die before reaching the age of 200 yearsyears

Strong and cogentStrong and cogent

Example 6Example 61.1. I know of three people who died in I know of three people who died in

traffic accidents due to injuries traffic accidents due to injuries sustained because they were sustained because they were wearing safety beltswearing safety belts

2.2. Ergo, it is safer not to wear a Ergo, it is safer not to wear a seatbelt while drivingseatbelt while driving

Weak and (cogent?)Weak and (cogent?)

Example 7Example 71.1. Every observed swan has been Every observed swan has been

white.white.2.2. Thus, all swans are white. Thus, all swans are white.

Is this a strong argument?Is this a strong argument? Is it cogent?Is it cogent?

Example 8Example 81.1. The first time I threw the dice, they came The first time I threw the dice, they came

up 10.up 10.2.2. The second time I threw the dice, they The second time I threw the dice, they

came up 2.came up 2.3.3. Given that I’ve thrown a 10 and a 2 on the Given that I’ve thrown a 10 and a 2 on the

previous two tries, it is more likely that I’ll previous two tries, it is more likely that I’ll throw a 7 or 11 (oh, craps!).throw a 7 or 11 (oh, craps!).

Is this a strong argument?Is this a strong argument? Is it cogent?Is it cogent?

Other CharacteristicsOther Characteristics Deductive arguments prove that a Deductive arguments prove that a

conclusion is true, but it gives us no new conclusion is true, but it gives us no new information about the world or particular information about the world or particular subject mattersubject matter

Inductive arguments can have true Inductive arguments can have true premises and a true conclusion, but the premises and a true conclusion, but the premises may not support the conclusion. premises may not support the conclusion. Also, a cogent inductive argument can Also, a cogent inductive argument can have true premises and a false conclusion, have true premises and a false conclusion, but remain cogentbut remain cogent

Example 9Example 91.1. Leibchen is a cat.Leibchen is a cat.2.2. All cats are animals.All cats are animals.3.3. Thus, Leibchen is an animal.Thus, Leibchen is an animal.

Is this a deductive or an inductive Is this a deductive or an inductive argument?argument?

If deductive, is it valid?If deductive, is it valid? If inductive, is it strong?If inductive, is it strong?

Example 10Example 101.1. Colder weather causes your furnace to run Colder weather causes your furnace to run

more often.more often.2.2. A furnace that runs more often causes you to A furnace that runs more often causes you to

have a higher gas bill.have a higher gas bill.3.3. So, Mother Nature should have to pay your So, Mother Nature should have to pay your

gas bill.gas bill.

Is this a deductive or an inductive argument?Is this a deductive or an inductive argument? If it’s deductive, then is it valid?If it’s deductive, then is it valid? If it’s inductive, then is it strong?If it’s inductive, then is it strong?

Example 11Example 111.1. All Bostonians have funny accents.All Bostonians have funny accents.2.2. Hence, we can suppose that the speech Hence, we can suppose that the speech

therapists there are not very good.therapists there are not very good.

Is this a deductive or an inductive Is this a deductive or an inductive argument?argument?

If it’s deductive, is it valid?If it’s deductive, is it valid? If it’s inductive, is it strong?If it’s inductive, is it strong?