Arguments byAnalogy

Chapter 10 Part 4

Remember “inductive reasoning”?

2© 2009 McGraw-Hill Higher Education. All rights reserved.

Inductive reasoningSUPPORTSrather thanDEMONSTRATES.

Generalizing supportsGENERAL statements.

GENERAL STATEMENTS areabout groups or “populations.”

How about statements aboutPARTICULARS?

How do you support them?

3© 2009 McGraw-Hill Higher Education. All rights reserved.

Hmmmm. Good question…

4© 2009 McGraw-Hill Higher Education. All rights reserved.

Cor

bis/

Pic

ture

Que

st

Often, throughARGUMENT BY ANALOGY!

5© 2009 McGraw-Hill Higher Education. All rights reserved.

Example>>>>>>>>>>>

“Nothing bad happened whenwe left Vietnam. So nothing badwill happen if we leave Iraq.”

6© 2009 McGraw-Hill Higher Education. All rights reserved.

“Saddam was just like Hitler.That’s why we had to take himout.”

7© 2009 McGraw-Hill Higher Education. All rights reserved.

“Her mom is a really nice. I’ll bether dad is, too!”

8© 2009 McGraw-Hill Higher Education. All rights reserved.

What do those three argumentshave in common?

9© 2009 McGraw-Hill Higher Education. All rights reserved.

“This is like that.Therefore, what holds for that will holdfor this.”

Leaving Iraq would be like leavingVietnam. Nothing bad happened whenwe left Vietnam. Therefore nothing badwill happen if we leave Iraq.

10© 2009 McGraw-Hill Higher Education. All rights reserved.

“X is like Y. Therefore, what holds for Ywill hold for X.”

“X” and “Y” are the “TERMS OF THEANALOGY.”

11© 2009 McGraw-Hill Higher Education. All rights reserved.

This is going to be fairly simple.

12© 2009 McGraw-Hill Higher Education. All rights reserved.

“Nothing bad happened when we leftVietnam. Therefore, nothing bad willhappen if we leave Iraq.”

How much SUPPORT does this offerfor thinking nothing bad will happen ifwe leave Iraq?

It depends on how SIMILAR the“terms of the analogy” are.

13© 2009 McGraw-Hill Higher Education. All rights reserved.

How similar THESE two terms areis debatable.That fact indicates the argumentoffers only modest support.

Therefore, a modest “confidencelevel” is called for >>>>>>>>>>>

14© 2009 McGraw-Hill Higher Education. All rights reserved.

© 2009 McGraw-Hill Higher Education. All rights reserved. 15

“Nothing bad happened when we left Vietnam.Therefore, nothing bad will happen if we leaveIraq.”

“Nothing bad happened when we leftVietnam. So it’s certainly possible nothingbad will happen if we leave Iraq.”

Safer formulation has modest confidence level:

Original formulation:

A good critical thinking habit:

16© 2009 McGraw-Hill Higher Education. All rights reserved.

Before you give an Argument by Analogy,ZERO-IN LIKE RADAR on the analogy, andLOOK FOR DIFFERENCES. Stick to SAFEconfidence-level indicators.

Let’s try a few….

“Bobo likes steak. So he issure to like carrots.”

NOT! Steak and carrots are WAY dissimilar,in terms of taste.

The argument offers ZERO support forthinking Bobo “is sure to like carrots.”

GoodAnalogy?

Don’t even worry about confidenceindicators for this argument; just throw it out.

17© 2009 McGraw-Hill Higher Education. All rights reserved.

Another:

“That guy will make an AWFUL dog owner.Just look at how he treats his kids!”

The “terms”?

How he treats his kids;how he will treat a dog.

Analogy good??

18© 2009 McGraw-Hill Higher Education. All rights reserved.

Good!

19© 2009 McGraw-Hill Higher Education. All rights reserved.

Children and dogs both experience pain andunhappiness. Treatment of either shouldreflect this.

Plus, generally people are even more carefulabout how they treat children.

The argument offers reasonable supportfor thinking this person would not make agood dog owner.

Hey, isn’t this pretty subjective?

20© 2009 McGraw-Hill Higher Education. All rights reserved.

Of course. There’s room for disagreement.

But reasonable people will agree: how totreat a dog is more like how to treat a childthan a steak is like a carrot.

“When he became president, Lincolnhad less political experience thanObama. And Lincoln was a great

president. So it is certainly possiblethat Obama could be an above-

average president despite lackingexperience.”The “TERMS”? Obama and Lincoln

It’d be hard to dispute such acautious conclusion.

Note the very low “confidence level.”

21© 2009 McGraw-Hill Higher Education. All rights reserved.

“She’s terrible at tennis, so Idoubt she’d be great at

racquetball.”

The terms? Her ability in tennis/her ability inracquetball

Confidenceindicator? “I doubt she’d be great”

Goodargument?

Not a perfect analogy, but theconfidence level seems right.

22© 2009 McGraw-Hill Higher Education. All rights reserved.

“Warren takes good care of his personalappearance. Let’s ask him to house sit for

us while we are in Europe.”

The terms? Warren’s treatment of his appearanceand his treatment of our house

Confidenceindicator?

High; speaker is willing to putmoney on it.

Good arg.?No! Poor analogy. It’s easier towash your face, etc., than to keepa house clean.

23© 2009 McGraw-Hill Higher Education. All rights reserved.

“Lysol kills germs, so it mightmake

a great deodorant.”

The terms? Lysol’s ability to kill germs: Lysol’sability as a deodorant.

Confidenceindicator?

“It might make” is relativelycautious.

Good arg.? Not! Poor analogy: the Lysol cansays, “not intended for personalhygiene”; a deodorant can doesn’t!

24© 2009 McGraw-Hill Higher Education. All rights reserved.

Yes. Reasonableanalogy. Moderateconfidence level.

“Babcock is a great senator; shemight well be a good president.”

The terms? B’s performance as senator;B’s performance as president.

Confidenceindicator?

Good argument?

25© 2009 McGraw-Hill Higher Education. All rights reserved.

“Hey, the ice caps on Mars are melting,and that isn’t due to fossil fuelemissions!! So melting ice caps herearen’t due to fossil fuel emissionseither!”

Good argument??

26© 2009 McGraw-Hill Higher Education. All rights reserved.

Earth and Mars are physically similar—a good reason to think ice caps COULDmelt on Earth in the absence of fossil fuelemissions.

On the other hand, it seems adoubtful reason for thinking fossilfuel emissions AREN’T a cause ofmelting here.

27© 2009 McGraw-Hill Higher Education. All rights reserved.

Arguments by analogy are ESPECIALLYimportant in four subjects:

The law

Moral philosophyHistory

Medical experiments

28© 2009 McGraw-Hill Higher Education. All rights reserved.

The only way to learn anythingfrom HISTORY is to see thesimilarities between pastevents and current events.

29© 2009 McGraw-Hill Higher Education. All rights reserved.

And one of the most important principles inLAW is stare decisis, “let the decision stand.”

“APPEAL TO PRECEDENT” in law isArgument by Analogy: If this case issufficiently similar to that earlier decision,then it must be decided the same…

…or the earlier decision must be shown tobe flawed.

30© 2009 McGraw-Hill Higher Education. All rights reserved.

A fundamental principle in ETHICS is thatsimilar cases must be treated similarly.

It would be WRONG to allow members ofthe women’s basketball team to make upa test and not allow members of themen’s baseball team to do that.

There is no RELEVANT difference betweenthe two cases.

31© 2009 McGraw-Hill Higher Education. All rights reserved.

Also, many MEDICAL EXPERIMENTSinvolve lab animals.

Whether the results apply to humansdepends on the strength of the analogybetween the lab animals and humananimals.

32© 2009 McGraw-Hill Higher Education. All rights reserved.

Recently the New Hampshire SupremeCourt ruled that a married woman’shaving a lesbian affair does NOTconstitute adultery.

The counter argument was that extramaritalsexual relationships, whether hetero- orhomosexual, are exactly the same in beingbetrayals, and therefore should be treatedsimilarly under law.

33© 2009 McGraw-Hill Higher Education. All rights reserved.

Determining whether two situations areanalogous can be so important we leave it tocourts to decide.

Moral: While analogical reasoninghas a subjective component, it isundeniably important and requirescareful deliberation.

34© 2009 McGraw-Hill Higher Education. All rights reserved.

Summary Analogy Argument by analogy Terms of the analogy Confidence level should reflect how

similar/dissimilar the terms are A subjective element is involved But reasonable people often agree on the

strength of analogy Argument by analogy is especially important in

ethical reasoning, legal reasoning, historicalreasoning, and medical experimentation.

35© 2009 McGraw-Hill Higher Education. All rights reserved.

Page 374, Exercise 10-3 Which of the first 8 items are

arguments by analogy?

36© 2009 McGraw-Hill Higher Education. All rights reserved.

Overall summary General statement

Generalizing

Sample

Target population

Feature

37© 2009 McGraw-Hill Higher Education. All rights reserved.

Summary continued Biased sample

Random sample

Confidence-indicator

Error margin-indicator

38© 2009 McGraw-Hill Higher Education. All rights reserved.

Summary continued Unclear generalizing

Hasty generalizing

Arguing from anecdote

Stereotype

Biased generalizing

Self-selected sample

Argument by analogy

Terms of the analogy

39© 2009 McGraw-Hill Higher Education. All rights reserved.