Find all School-related info fast with the new School-Specific MBA Forum

It is currently 21 Aug 2014, 17:58

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A logical fallacy is an error of reasoning. It either has

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
14 KUDOS received
SVP
SVP
User avatar
Joined: 03 Jan 2005
Posts: 2255
Followers: 12

Kudos [?]: 195 [14] , given: 0

GMAT Tests User
A logical fallacy is an error of reasoning. It either has [#permalink] New post 21 Dec 2006, 12:06
14
This post received
KUDOS
9
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:00) wrong based on 5 sessions
A logical fallacy is an error of reasoning. It either has an error in the logical structure of deduction (formal fallacy), or is falsely inducted from one or more of its premises (informal fallacy).

I will list a few common fallacies here.

Questionable Cause
Circular reasoning
In the fallacy of circular reasoning, you assume to be true what you are supposed to be proving.
This product is the best because it is better than any other products.
A more complicated example:
A: This product is perfect.
B: But there is an article in yesterday’s newspaper saying that there is a defect in this product.
A: That article must be wrong. How could a perfect product have a defect?


Post hoc reasoning
Also called false cause reasoning. It argues because A preceded B, therefore A caused B.
All plants that survive in metal soils produce histidine. Histidine must be the reason that they can survive the harmful soil.
My red shirt is lucky. Every time I wear it in a soccer game my team wins.

A related fallacy is called Gamblers fallacy:
An argument that assumes that a departure from what occurs on average or in the long term will be corrected in the short term.
In a coin toss experiment, the result for the first five throw is head. Therefore we have a very high probability of getting a tail in the six throw.

Slippery slope
An argument that falsely assume that one thing must lead to another.
Company A has been growing much faster than company B in the past five years. Soon A will surpass B.
You can never give anyone a break. If you do, they'll walk all over you.


Loaded questions
A question constructed in such a way that agreement or disagreement with one term seems to imply agreement with the second.
Are you going to admit that you’re wrong?
Have you enjoyed spoiling the dinner for everybody?

Informal Relevance Fallacy
Argument by authority
An argument that bases the judgment of an assertion on the source of the assertion.
This medicine is effective because my doctor said so.
A related fallacy is sometimes called Personal attack, in which one dispute an argument based on the source of the argument.
Jerry recommended this milk. But I distrust Jerry. So I won’t buy this milk.

Appeal to common belief
A fallacious argument that concludes a proposition to be true because many or all people believe it.
Since 60% of the people polled believed in the Bible, the Bible must be true.
Fifty million Elvis fans can't be wrong.
Doctors recommended this medicine than any other medicine. You should buy it.
Brand X vacuums are the leading brand in America. You should buy Brand X vacuums.


A similar type of fallacy is Appeal to tradition:
A common logical fallacy in which someone proclaims his or her accuracy by noting that "this is how it's always been done."
This is right because we've always done it this way.
Your invention is a bad idea because it has no historical precedent.


Argument from ignorance
A logical fallacy in which it is claimed that a premise is true only because it has not been proven false, or that a premise is false only because it has not been proven true.
Nobody has seen it. It could not have happened.

It’s similar to Shifting the Burden of Proof
The God exist. Unless you can prove that the God doesn’t exist, you have to accept it as the truth.

It’s also similar to Argument from incredulity
What he said is very hard to believe. It simply cannot be true.

Faulty Generalization
Hasty generalization
An argument that bases a generalization on insufficient number of instances.
The weather must be perfect in San Diego all the time. I’ve been there several times, and the sky was always blue and the temperature ideal.
Three of my patients have been harmed by this vaccine. It must be unsafe.


A reverse type of fallacy is Sweeping generalization, which applies a general rule to a specific case.
Our GMAT class has raised the participants an average of 100 points in their GMAT scores. You had a GMAT score of 600 and have taken our class. You will score 700 in your next attempt for sure.

Biased sample
The conclusion is drawn based on a biased sample that is not representative of the entire population.
I can’t believe our restaurant isn’t the best in town. All our regular customers love us.

Propositional Fallacies
the fallacy of the alternative disjunct
A or B
A
Therefore not B
Number x belongs to a set that contains numbers that are multiples of 2 or 3. It is a multiple of 2, therefore it must not be a multiple of 3.

Affirming the consequent
If P, then Q.
Q.
Therefore, P.
All humans are mortal. Meow is mortal. She must be a human. (She could be a cat.)

Argument from fallacy
If A then B
Not A
Therefore not B
I close my eyes when I’m sleeping. I’m not sleeping, so my eyes must not be closed.
When I was little I was told that an Angel always pushes a dropped pencil down to the floor. Now I know that angels do not exist. Therefore a pencil will never drop down to the floor.
_________________

Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.


Last edited by HongHu on 21 Dec 2006, 12:48, edited 1 time in total.
Kaplan Promo CodeKnewton GMAT Discount CodesManhattan GMAT Discount Codes
3 KUDOS received
Director
Director
avatar
Joined: 28 Dec 2005
Posts: 922
Followers: 2

Kudos [?]: 37 [3] , given: 0

GMAT Tests User
 [#permalink] New post 29 Dec 2006, 07:34
3
This post received
KUDOS
Thanks for starting this post HongHu. I found this in another part of this forum that I think best belongs here.
Attachments

logical_fallacies.doc [86 KiB]
Downloaded 1871 times

To download please login or register as a user

2 KUDOS received
SVP
SVP
User avatar
Joined: 03 Jan 2005
Posts: 2255
Followers: 12

Kudos [?]: 195 [2] , given: 0

GMAT Tests User
 [#permalink] New post 30 Dec 2006, 00:01
2
This post received
KUDOS
That's great! Thanks hsampath!

here is a more detailed coverage of Logical Fallacies
Attachments

fallacies.pdf [603.23 KiB]
Downloaded 1769 times

To download please login or register as a user


_________________

Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.

Manager
Manager
User avatar
Joined: 07 Jun 2009
Posts: 213
Followers: 1

Kudos [?]: 21 [0], given: 9

GMAT Tests User
Re: Logical Fallacies - help on CR and AWA [#permalink] New post 12 Jun 2009, 09:19
Commendable effort HongHu...Thank you..
_________________

"Always....Read between the lines"

Intern
Intern
avatar
Joined: 02 Oct 2009
Posts: 15
Followers: 0

Kudos [?]: 2 [0], given: 15

Re: Logical Fallacies - help on CR and AWA [#permalink] New post 08 Nov 2009, 07:48
great post :)
Senior Manager
Senior Manager
User avatar
Joined: 22 Dec 2009
Posts: 365
Followers: 10

Kudos [?]: 201 [0], given: 47

GMAT ToolKit User GMAT Tests User
Re: Logical Fallacies - help on CR and AWA [#permalink] New post 01 Jan 2010, 04:31
Perfect Master piece!!! Thanks HongHu and others!

Cheers! :punk
JT
_________________

Cheers!
JT...........
If u like my post..... payback in Kudos!! :beer

|Do not post questions with OA|Please underline your SC questions while posting|Try posting the explanation along with your answer choice|
|For CR refer Powerscore CR Bible|For SC refer Manhattan SC Guide|


~~Better Burn Out... Than Fade Away~~

SVP
SVP
User avatar
Joined: 01 Oct 2013
Posts: 1643
Followers: 229

Kudos [?]: 50 [0], given: 0

Premium Member
Re: A logical fallacy is an error of reasoning. It either has [#permalink] New post 12 Nov 2013, 23:51
Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Re: A logical fallacy is an error of reasoning. It either has   [#permalink] 12 Nov 2013, 23:51
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic Logical Fallacies - great overview Skientist 2 19 Sep 2012, 05:49
logic reasoning questions fionaramusane 0 02 Dec 2009, 22:25
reasoning error Dan 3 07 Jul 2005, 05:53
Common patterns of fallacious reasoning are endemic to chunjuwu 4 06 Mar 2005, 19:08
Logical Fallacy? michalky 1 09 Oct 2004, 12:31
Display posts from previous: Sort by

A logical fallacy is an error of reasoning. It either has

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.