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Fallacies
by Dagny Taggart - Friday, 25 April 2008, 12:28 AM
  cat 2008 cat 2009 xat 2008 cat coaching cat training cat papersFor all CAT 2008 aspirants who love to argue among their friends, here is a potent weapon to hone their reasoning skills. A knowledge of errors that we commit while making arguments will prevent us from committing them. A fallacy is an error in reasoning where the argument fails to establish the truth because it relies on premisses that do not imply the conclusion. In a fallacious argument, the conclusion could be false even if all its premisses were true. Therefore, a fallacy is an argument which may seem to be correct but is not so. Aristotle, in his Sophistical Refutations (Sophistici Elenchi), identified thirteen fallacies. Today, a list of more than 100 has been developed.

 

 


Fallacy of the Consequent or the If-then fallacy:

Fallacy of the consequent draws a conclusion from premises that do not support that conclusion. The fallacy is based on the following argument:

cat

Only two valid reasoning can be made out of this argument:

cat 2008

If it rains, peacock will dance.

There will be hypothetical deductions from this statement:

  1. It rains
  2. It does not rain
  3. Peacock dances
  4. Peacock does not dance

1)     It rains- If this statement is true, then peacock will dance.
2)    
If it does not rain- From this statement, we can deduce nothing because it is not necessary that peacock dances only when it rains. There can be other reasons why a peacock may dance.
3)    
If peacock dances- From this statement also we can deduce nothing because peacock can dance even when it does not rain.
4)    
If peacock does not dance- From this statement it can be deduced that it has not rained for sure.  Because, had it rained, peacock would have danced for sure.

From the following example, we are sure of 2 things-

1)     What will happen if A occurs.
2)    
What happened if B did not occur.

Embedded if-then statements:

The pattern

A only if B â‡’ If A then B.

cat 2008

Ram and Shyam both cannot dance.

From the above statement, two conclusions can be drawn.

1)     If Ram dances, then Shyam cannot dance.
2)    
If Shyam dances, then Ram cannot dance.

I will go to Goa only if I have enough money.

Correct Interpretation:

If I go to Goa, then for sure I have enough money.

Incorrect Interpretation:

If I have enough money, then I will go to Goa.

The only surety that we get from the main statement is that if I went to Goa then I had enough money.

Fallacy of accident/Hasty Generalization:

This fallacy is committed when assumptions are made based on a sample, which is either inadequate or incomplete. The Fallacy of Accident is committed when a general rule is applied to a particular case.

My friend said her mother is strict.
My mother is also strict.
All mothers must be strict.

This is a faulty generalization because I am making a biased conclusion based on a small sample. Many mothers may not be strict at all.

I have tasted 3 ice-creams from Wality Qualls.
I didn’t like the taste of all three.
Therefore, the ice-creams from Wality Qualls are bad.

The conclusion is fallacious because the three ice-creams that I didn’t like may be liked by someone else. But the generalization that the ice-creams from Wallity Qualls are bad is wrong.

Tu Quoque Fallacy:

Tu Quoque means ‘you too’. This type of argument is focused on the personal character of the opponent. Here the arguer points out that the opponent’s opinion are not be trusted because the opponent has actually done something he/she is arguing against. This fallacy attempts to show that a criticism or objection applies equally to the person stating it.

The pattern

A makes criticism B.
A is also guilty of B.

Therefore, B is false.

      Mom: Rohan, don’t smoke. It is harmful for your health.
      Rohan: I will smoke because you too smoked when you were of my age.

Here Rohan’s response is fallacious because the fact that Rohan’s mom has done something that she is comdemning Rohan to do has no bearing on the premise that she puts forward in her argument. (i.e. Smoking is harmful for health)

Q: Now, the United States government says that you are still funding military training camps here in Afghanistan for militant, Islamic fighters and that you're a sponsor of international terrorism.… Are these accusations true? …

Osama Bin Laden: …At the time that they condemn any Muslim who calls for his right, they receive the highest top official of the Irish Republican Army at the White House as a political leader, while woe, all woe is the Muslims if they cry out for their rights. Wherever we look, we find the US as the leader of terrorism and crime in the world. The US does not consider it a terrorist act to throw atomic bombs at nations thousands of miles away, when it would not be possible for those bombs to hit military troops only. These bombs were rather thrown at entire nations, including women, children and elderly people and up to this day the traces of those bombs remain in Japan. The US does not consider it terrorism when hundreds of thousands of our sons and brothers in Iraq died for lack of food or medicine. So, there is no base for what the US says and this saying does not affect us.…

Ad Hominen Fallacy:

Ad Hominen means ‘against the person’. This fallacy is committed based on the person’s personal character rather than on evidence or conclusion. In this kind of argument, the opponent is attacked rather than his statements. Participants in heated conversation sometimes disparage the character of their opponent and question their integrity. But the character of an individual is logically irrelevant to the truth or falsity of his argument or reasoning.

The pattern

1.      Person A makes claim X.
2.     
Person B makes an attack on person A.
3.     
Therefore A's claim is false.

Jane has written many books on feminism and female infanticide. But I do not trust her writings because she was convicted for felony drug addiction when she was young.

Circular Reasoning/ Begging the question / petitio principii:

Petitio principii is a Latin phrase meaning begging or taking for granted of the beginning or of a principle. This fallacy is committed when one assumes the claim to be true what one is proving. It is essentially repeating the statement in different or stronger terms. This logical fallacy attempts to undermine a speaker's argument by attacking the speaker instead of addressing the argument.

"Dear Friend, a man who has studied law to its highest degree is a brilliant lawyer, for a brilliant lawyer has studied law to its highest degree."  Oscar Wilde, De Profundis.

In the above example the conclusion has been assumed in the premise itself that Cricket has the biggest fan following in the world without even proving or putting forward the essential facts. The statement by Rob is actually the restatement of what Richard has claimed.

The pattern:

  • A implies B

  • suppose A

  • Therefore, B. OR A is B, therefore A is B.

"You know that God is a just and loving God because God is God and cannot be unjust or unloving."

The second claim does not offer any evidence; it is essentially repeating the premise.

Weak or Faulty Analogy/ Ceteris Paribus Assumption/ Questionable Analogy / Faulty Analogy / Vague Similarities /Extended Analogy/ Faulty Comparison/ False Metaphor:

Ceteris Paribus means with other things being the same. In faulty/weak analogy, an argument takes place between two or more things, situations or ideas. The argument is taken for granted that since a few things are same, the rest of things would also be the same.

The pattern :

A and B are similar.
B has property X.
Therefore, A has property X.

Eg. Railways are like airlines.
     Both are modes of transportation.
     Since railways have lower fares, airlines should also have lower fares.

The conclusion is fallacious because the arguer is not considering many other factors into consideration for airlines charging higher fares.

Eg. Giraffes have fur, eat plants, and have names that start with G.
Guinea pigs also have a name that starts with a G, have fur, and eat plants.
Guinea pigs are also probably very large.

Ad Populam:

This Latin phrase means ‘to the people’. This fallacy is committed when the arguer tries to convince the audience by putting the desires or likes of most of the people and ultimately convincing the audience to believe something because ‘everyone else does.’ The basis of the ad populum appeal is the assumption that large numbers of audience is more likely to be right than you are likely to be right.

The Pattern

Most, many, or all persons approve of statement A.
Statement A is true.

Eg: 70% of Indians agree that they become lazy during the winters. So, winters are a season of laziness.

The conclusion is fallacious because the arguer is trying to convince that because 70% Indians agree to a common cause, it must be taken true for all. Always remember that it is good to keep a popular opinion but it may not be right always.

This fallacy is also commonly used for marketing and advertising purposes:

Sony. Ask anyone.
Fifty million Elvis fans can't be wrong.

                                                cat 2008

False cause/ Post Hoc:

Post hoc is taken form  a Latin phrase ‘ Post hoc ergo propter hoc. It means ‘after this, therefore, because of this. The fallacy takes place because of mere proximity of time.  Assuming that B comes after A, A caused it.

The Pattern:

  1. A occured just before B.

  2. Therefore A caused B.

The only policy that effectively reduces public shootings is right-to-carry laws. Allowing citizens to carry concealed handguns reduces violent crime. In the 31 states that have passed right-to-carry laws since the mid-1980s, the number of multiple-victim public shootings and other violent crimes has dropped dramatically. Murders fell by 7.65%, rapes by 5.2%, aggravated assaults by 7%, and robberies by 3%.

The statement is fallacious because crimes may have dropped because of some other reasons but the arguer has overlooked them and assumed that B comes after A so, A caused it.

Straw Man:

In this fallacy, the arguer attributes an argument to the opponent that does not represent opponent’s true position. The arguer sets up an untrue version of the opponent’s position. To "set up a straw man" or "set up a straw man argument" is to describe a position that superficially resembles an opponent's actual view but is easier to refute, then attribute that position to the opponent (for example, deliberately overstating the opponent's position).

The pattern:-

  1. Person A has position X.

  2. Person B presents position Y (which is actually the distorted version of X).

  3. Person B attacks position Y.

  4. Therefore X is false/incorrect/flawed.

Animal lovers want ban on using leather items.

This argument is fallacious because many animal lovers may themselves be using leather items and their love for animals may be restricted to stray animals.

cat 2008

‘All things are equal’ Fallacy:

This fallacy is committed when it is assumed that the background conditions have remained same irrespective of place, situation, or time.

Eg. Rashi stood first in class last year.
     She will stand first this year as well.

The argument is fallacious because the arguer has overlooked that factors that may go against Rashi standing first in the class this year as well. The factors may range from Rashi not have worked hard enough this year or she might have fallen ill because of which she couldn’t prepare much etc.

Fallacy of Equivocation:

The term equivocation comes from the Latin terms equi (equal) and vox (voice) - and means "with equal voice .This fallacy is committed when a phrase/ word has more than one meaning but the word/ phrase slides between the different meanings that are important according to the context of the argument.

The Pattern:

a.      Premise: Statement(s) using term A in sense 1
b.     
Premise: Statement using term A in sense 2
c.     
AND/OR Conclusion: Statement using term X in sense 2

Eg. Jam is better than nothing
Nothing is better than butter
Therefore jam is better than butter

This equivocation exploits two different meanings of the word "nothing" to come to an apparent conclusion about the relative merits of two different things without actually making reference to any of their respective merits. In the first statement, "nothing" really means "dry bread" (such that the sentence means "it is preferable to have jam [on bread] than nothing at all"), whereas in the second, it means, literally, "no thing" (so the sentence means "there exists no thing that is better than butter").

cat 2008

Non Sequitor:

Non Sequitor means ‘does not follow’. This fallacy is committed when the conclusion does not strictly follow from the premises. The premises have no direct relationship to the conclusion.

Eg. Abhinav is tall, he must be fat.

The statement is fallacious because Abhinav’s being tall does not qualify that he is fat.
Rhea will stand first in class because she has put in lot of efforts.

The argument does not consider that someone else might be better than Rhea or Rhea must have put in lot of efforts but have not written her answers well in her exams etc.

Re: Fallacies
by ashish singh - Friday, 25 April 2008, 03:42 AM
 

hi ma'm,

gr8 article...

i have a doubt regarding Post hoc/false cause.Can we aplly these logics to RCs like if the following passage is a RC

" The only policy that effectively reduces public shootings is right-to-carry laws. Allowing citizens to carry concealed handguns reduces violent crime. In the 31 states that have passed right-to-carry laws since the mid-1980s, the number of multiple-victim public shootings and other violent crimes has dropped dramatically. Murders fell by 7.65%, rapes by 5.2%, aggravated assaults by 7%, and robberies by 3%"

Q. what can be conclueded form the passage?

ans: The crime rate fell because of the 'right-to-carry'.

Isn't this concluesion correct???

 

Re: Fallacies
by Dagny Taggart - Friday, 25 April 2008, 06:17 AM
  Hi Ashish,

Fallacies are a part of critical reasoning. Let's see another example- You entered in, Sachin got out. The statement is fallacious because the arguer is not considering that Sachin may have got out because of some other reason.

In the above example the arguer is assuming that the violence came down at the same rate in the states that did not pass "right-to-carry" laws. We do not have the figures for these states. So, the comparison cannot be made.Also, the violence may have came down for some other reasons. But since "right-to-carry" laws were passed in the same year, the aruger is assuming that there can be no other reason for the violence to come down.
Superstition is also a part of Post Hoc Fallacy.
Re: Fallacies
by aspirant cat - Friday, 25 April 2008, 10:00 AM
 

Hi maam,

really nice article and one must say very informative both philosophically and in also fits well in literature point of view; it clearly explains  things which were till now not understood well. One spell mistake i guess shouldn't it be "Ad Hominem"thoughtful... and one more thing, the second last fallacy Fallacy of Equivocation: isnt it more about word play than the actual undersanding/putting forth arguments or things related to logics. May be the example given, provides the explanation to meaning of logic rather than spirit of the fallacy. Could you please explain it in a one more different way ??

thanks a lot for the pain taken and great job done

rgds

ac

 

Re: Fallacies
by ashish singh - Friday, 25 April 2008, 05:35 PM
  thank u ma'm for clearing my doubt AT 6.17 AM!!!!!!!surprise
Re: Fallacies
by Dagny Taggart - Friday, 25 April 2008, 08:09 PM
 

Hi AC,

Let’s look at this example:

Giving money to Tsunami victims is a right thing to do.
So, Tsunami victims have right to our money.

Now, look at the meaning of right both the statements:

Right- In statement 1, ‘right’ means the act of doing something correct/good.

Right- In statement 2 , ‘right’ means an entitlement to have something.

And thanks for the correction. It should be Ad Hominem.smile

Ashish,

Are you thanking me that I cleared your doubt or that I cleared your doubt at 6.17a.m? tongueout

Dagny


Re: Fallacies
by Total Gadha - Friday, 25 April 2008, 08:15 PM
  smile
Re: Fallacies
by ashish singh - Friday, 25 April 2008, 09:27 PM
  bothbig grin
Re: Fallacies
by Gargi Bhatt - Saturday, 26 April 2008, 11:42 AM
 

Real good article maam , loved it.. thanks a lot smile

Re: Fallacies
by anil kumar - Sunday, 27 April 2008, 10:01 PM
  thanks mam, even though i did course on symbolic logic long ago(and i forgot almost all), i can recollect many things now after reading this article. Thanks a ton!!!!
Re: Fallacies
by Santhosh Kumar - Tuesday, 29 April 2008, 12:45 AM
 

Respected DG mam,

How are you ?

Very useful  article.

- San

Re: Fallacies
by Dagny Taggart - Tuesday, 29 April 2008, 07:04 AM
  Hi Santhosh,

From the time we have started tg, there has only been one student who has addressed me as DG. Well! his name was also Santhosh and he was a last year student.I don't know whether you are the same student but anyways, Thanks.smile

Thank you all.smile
Re: Fallacies
by ATOM ANT - Thursday, 1 May 2008, 09:12 PM
  Nice article madam.smile Thanks for it.
Re: Fallacies
by Total Gadha - Friday, 2 May 2008, 12:36 PM
  Hi AC,

Here's a joke for you on Fallacy of Equivocation

Mulla Nasruddin sat on a river bank when someone shouted to him from the opposite side:
- "Hey! how do I get to the other side?"
- "You are on the other side!" Nasruddin shouted back.

Total Gadha
Re: Fallacies
by ATOM ANT - Friday, 2 May 2008, 01:00 PM
  smile
Re: Fallacies
by Ajit kumar - Saturday, 3 May 2008, 01:56 PM
  big grin
Re: Fallacies
by mayank gupta - Wednesday, 21 May 2008, 01:59 AM
 

Hi Dagny i'm not able to understand this;

 

Embedded if-then statements:

The pattern

A only if B â‡’ If A then B.

cat 2008

But Logic table of A -> B should be 

A B →
T T T
T F F
F T T
F F T

pls correct me if i'm wrong

Re: Fallacies
by Dagny Taggart - Wednesday, 21 May 2008, 01:20 PM
  Hi Mayank,

Thanks for bringing this in notice; have corrected the chart.
Explanation:-

  • If the premises are false and the inference valid, the conclusion can be true or false. (1&4)
  • If the premises are true and the inference valid, the conclusion must be true. (1)
  • If the premises are true and the conclusion false, the inference must be invalid.(3)
Re: Fallacies
by mayank gupta - Saturday, 24 May 2008, 11:52 AM
 

Hi Dagny

I'm preparing for the gmat. After many test and practice i'm still struggling with my CR. Sorry to discuss it at the wrong place, but it will be helpful if you can point me to some document or suggest some strategy (apart from reading carefully, which i always do) to improve my CR. CR has bacome a cause of worry to me. Please suggest.

Thanks                                                                                                                    

Mayank

 

Re: Fallacies
by Dagny Taggart - Saturday, 24 May 2008, 01:30 PM
  Hi Mayank,

Please follow the link :http://totalgadha.com/mod/forum/discuss.php?d=2808

Also, you can download Dagny Taggart's file to GMAT from Download it Now section.
Re: Fallacies
by mayank gupta - Sunday, 25 May 2008, 12:27 AM
  Thnx Dagny.thnxs a ton...i'm goin through it if some problem comes i'l revert to you
Re: Fallacies
by Ashwin Doke - Monday, 26 May 2008, 05:15 PM
  Dear Ma'm,

really enjoyed this article.

I m new on TG ( & actually should be the guy with patency of literally being a Total G ) [big grin]

Its fun growing stronger this way.


Regards,
Ashwin
Re: Fallacies
by ankita agarwal - Tuesday, 27 May 2008, 01:50 PM
  hii mam...d article is awesome....now my many doubts r cleared...but i still didnt understood "straw man fallacy"...can u plss explain it by any other example...
Re: Fallacies
by Varun Goenka - Wednesday, 4 June 2008, 03:37 PM
 

hey dagny ,

gr8 article...

wud lik 2 thank u n TG 4 dis wonderful site...m writin 4 d 1st time on ur site bt hv been followin it since a month or so...it is f gr8 help 4 all CAT aspirants...

gr8 goin...keep up ur gud wrk...hats off

Re: Fallacies
by ashutosh pathak - Saturday, 7 June 2008, 04:29 AM
 

hi mam

can u plz tell suggest me any good book for quant...

i want to brish up my fundas.....

Re: Fallacies
by Sneha Sinha - Monday, 9 June 2008, 12:32 PM
 

Hi Dagny,

When will u start i RC everyday like last year. Plz start it as soon as possible. Its already June.

sneha

Re: Fallacies
by Dagny Taggart - Tuesday, 10 June 2008, 11:30 PM
  Sneha ,

I have already posted some 94 RCs for CAT 2008 students. Please visit CAT Verbal Forum.
Re: Fallacies
by whirl wind - Wednesday, 6 August 2008, 02:34 PM
 

Dagny,

 

"Animal lovers want ban on using leather items.

This argument is fallacious because many animal lovers may themselves be using leather items and their love for animals may be restricted to stray animals. "

This is straw man fallacy....But arent we committing Tu Quoque Fallacy by stating that they themselves are using those leather items or because their love is restricted to stray animals..??

any fallacy in this..???

Re: Fallacies
by Anoop Kothari - Saturday, 5 September 2009, 07:07 PM
  Hi Taggart,
this is my first reply or doubt in this Gadha land.

I will go to Goa only if I have enough money.

Correct Interpretation:

If I go to Goa, then for sure I have enough money.

Incorrect Interpretation:

If I have enough money, then I will go to Goa.

The only surety that we get from the main statement is that if I went to Goa then I had enough money.

here you are saying the thing which is true for
A If B
but in Example it is
A only if B
Can you explain the diff.between two Condition.

@n00p
Re: Fallacies
by lazy gadha - Tuesday, 5 October 2010, 03:49 PM
 

thanks mam

i's just say it is awesome