TagLast edit: 2 Mar 2021 18:04 UTC by Yoav Ravid

A fallacy is generally considered to be an error in reasoning. It refers both to the failure to apply logic to a line of thought, and to the use of problematic arguments. The term can be applied when dealing both with informal and formal logic, although it usual refers to the former.

Related: Disagreement, Heuristics & Biases

Informal vs Formal Fallacy

An informal fallacy refers to a flawed argument, where the premises do not support the conclusion. It can, however, have a valid logical format. This type of fallacy is commonly divided in two main groups: material fallacies and verbal fallacies.

Material fallacies, concerned with the content of the argument, can be divivided following Aristotle’s taxonomy from his work Organon. One such example is the famous Straw Man fallacy:

  1. Person A has position X: We should focus our efforts on Friendly AI research.

  2. Person B distorts position X to something close, but different, Y: So you think we should just give up on webdesign?!

  3. Person B attacks position Y: That’s stupid, websites are such a great way of spreading information!

Verbal fallacies, on the other hand, deal with the way the words are used. These include examples such as Equivocation—using words ambiguously or with double meanings—and Proof by Verbosity, where one overwhelms his listener with lots of material in an complicated way.

A formal fallacy, contrasting with informal fallacies, refers to a pattern of reasoning which is wrong due to a flaw in the logical structure of the argument. As such, this deductive fallacy does not imply any information about the premises or the conclusion—its their connection that’s wrongly stated. Both can be correct and the argument can be wrong because the conclusion doesn’t follow from the premises as it is said to.

False Fallacies & Awareness

Matters can be further complicated by arguing parties incorrectly claiming that an assertion is false due to a fallacy. For example, if one party was to declare “Albert Einstein has claimed that time and space are relative qualities of the Universe.”, another party might responded by saying that this is an ’’’argument from authority’’’. However, Albert Einstein’s claims are based on detailed mathematical models that identify him as an expert in this field of inquiry, rather than a casual observer. We are thus facing a kind of meta-fallacy which is wrong by itself.

Recognizing fallacies in everyday arguments can be difficult due to complicated patterns of communication that mask the logical connections between statements. At the same time, informal fallacies can also take advantage of the emotional or psychological weaknesses of the listener. It is thus important to develop the ability to recognize them in arguments, so as to reduce the likelihood of being tricked or cheated. This ability becomes even more important when dealing with today’s mass media, where the intention is to influence behavior and change beliefs, from political campaigns to simple local newspapers.

Further Reading & References

See Also

Know­ing About Bi­ases Can Hurt People

Eliezer Yudkowsky4 Apr 2007 18:01 UTC
135 points
80 comments2 min readLW link

Con­junc­tion Fallacy

Eliezer Yudkowsky19 Sep 2007 1:54 UTC
41 points
46 comments3 min readLW link

Prov­ing Too Much

Scott Alexander14 Apr 2013 0:05 UTC
53 points
1 comment2 min readLW link

The Fal­lacy of Gray

Eliezer Yudkowsky7 Jan 2008 6:24 UTC
179 points
78 comments5 min readLW link

The non­cen­tral fal­lacy—the worst ar­gu­ment in the world?

Scott Alexander27 Aug 2012 3:36 UTC
280 points
1,754 comments7 min readLW link

Mind Pro­jec­tion Fallacy

Eliezer Yudkowsky11 Mar 2008 0:29 UTC
58 points
90 comments2 min readLW link

Plan­ning Fallacy

Eliezer Yudkowsky17 Sep 2007 7:06 UTC
105 points
45 comments3 min readLW link

Bur­den­some Details

Eliezer Yudkowsky20 Sep 2007 23:46 UTC
118 points
33 comments4 min readLW link

The Third Alternative

Eliezer Yudkowsky6 May 2007 23:47 UTC
95 points
83 comments3 min readLW link

The Log­i­cal Fal­lacy of Gen­er­al­iza­tion from Fic­tional Evidence

Eliezer Yudkowsky16 Oct 2007 3:57 UTC
84 points
58 comments6 min readLW link

The Ge­netic Fallacy

Eliezer Yudkowsky11 Jul 2008 5:47 UTC
42 points
16 comments3 min readLW link

The Com­plete Idiot’s Guide to Ad Hominem

Eliezer Yudkowsky25 Nov 2008 21:47 UTC
13 points
15 comments1 min readLW link

The Truth about Scots­men, or: Dis­solv­ing Fallacies

Tesseract5 Dec 2010 21:57 UTC
37 points
36 comments3 min readLW link

Gen­er­al­iz­ing From One Example

Scott Alexander28 Apr 2009 22:00 UTC
350 points
412 comments6 min readLW link

Defend­ing the non-cen­tral fallacy

Matthew Barnett9 Mar 2021 21:42 UTC
107 points
39 comments6 min readLW link

Catchy Fal­lacy Name Fal­lacy (and Sup­port­ing Disagree­ment)

JGWeissman21 May 2009 6:01 UTC
32 points
57 comments2 min readLW link

Fal­la­cies as weak Bayesian evidence

Kaj_Sotala18 Mar 2012 3:53 UTC
79 points
41 comments10 min readLW link

I Was Not Al­most Wrong But I Was Al­most Right: Close-Call Coun­ter­fac­tu­als and Bias

Kaj_Sotala8 Mar 2012 5:39 UTC
86 points
40 comments9 min readLW link

Car­diol­o­gists and Chi­nese Robbers

Scott Alexander16 Sep 2015 19:00 UTC
81 points
4 comments6 min readLW link

Your in­tu­itions are not magic

Kaj_Sotala10 Jun 2010 0:11 UTC
129 points
36 comments4 min readLW link

What cog­ni­tive bi­ases feel like from the inside

chaosmage3 Jan 2020 14:24 UTC
201 points
25 comments4 min readLW link

Talk­ing Snakes: A Cau­tion­ary Tale

Scott Alexander13 Mar 2009 1:41 UTC
145 points
230 comments3 min readLW link

[Question] Can So­cial Dy­nam­ics Ex­plain Con­junc­tion Fal­lacy Ex­per­i­men­tal Re­sults?

curi5 Aug 2020 8:50 UTC
8 points
8 comments1 min readLW link

Re­sist the Happy Death Spiral

Eliezer Yudkowsky4 Dec 2007 1:15 UTC
49 points
36 comments6 min readLW link

The Haters Gonna Hate Fallacy

Kaj_Sotala22 Sep 2020 12:20 UTC
46 points
6 comments1 min readLW link

Pain is not the unit of Effort

alkjash24 Nov 2020 20:00 UTC
312 points
70 comments5 min readLW link

Fu­sion and Equiv­o­ca­tion in Korzyb­ski’s Gen­eral Semantics

abramdemski21 Dec 2020 5:44 UTC
59 points
12 comments3 min readLW link

[Question] look­ing for name/​fur­ther read­ing on fal­lacy I came across

Yitz28 May 2020 18:01 UTC
1 point
1 comment1 min readLW link

Hind­sight De­val­ues Science

Eliezer Yudkowsky17 Aug 2007 19:39 UTC
157 points
40 comments2 min readLW link

The Typ­i­cal Sex Life Fallacy

ozymandias7 Oct 2017 21:48 UTC
27 points
293 comments5 min readLW link

Make your train­ing useful

AnnaSalamon12 Feb 2011 2:14 UTC
127 points
48 comments5 min readLW link

The Ep­silon Fallacy

johnswentworth17 Mar 2018 0:08 UTC
49 points
11 comments7 min readLW link

The Pas­cal’s Wager Fal­lacy Fallacy

Eliezer Yudkowsky18 Mar 2009 0:30 UTC
37 points
128 comments3 min readLW link

The Statis­ti­cian’s Fallacy

ChrisHallquist9 Dec 2013 4:48 UTC
63 points
69 comments3 min readLW link

Dialogue on Ap­peals to Consequences

jessicata18 Jul 2019 2:34 UTC
33 points
82 comments7 min readLW link

Hy­po­thet­i­cals: The Direct Ap­pli­ca­tion Fallacy

Chris_Leong9 May 2018 14:23 UTC
21 points
19 comments4 min readLW link

Surely, rhetor­i­cal ques­tion?

Gust11 Jan 2018 20:56 UTC
15 points
0 comments1 min readLW link

The Sally-Anne fallacy

philh11 Apr 2016 13:06 UTC
51 points
30 comments1 min readLW link

Three Fal­la­cies of Teleology

Eliezer Yudkowsky25 Aug 2008 22:27 UTC
36 points
16 comments9 min readLW link

Flow­sheet Logic and Note­card Logic

moridinamael9 Sep 2015 16:42 UTC
44 points
28 comments3 min readLW link

A Model of Ra­tional Policy: When Is a Goal “Good”?

FCCC10 Oct 2020 17:05 UTC
2 points
0 comments17 min readLW link

[Question] Is Stu­pidity Ex­pand­ing? Some Hy­pothe­ses.

David_Gross15 Oct 2020 3:28 UTC
68 points
42 comments4 min readLW link

Imag­i­nary Positions

Eliezer Yudkowsky23 Dec 2008 17:35 UTC
28 points
49 comments3 min readLW link

The Fal­lacy of Dress­ing Like a Winner

benelliott26 Dec 2010 20:59 UTC
27 points
21 comments6 min readLW link

Why *I* fail to act rationally

bentarm26 Mar 2009 3:56 UTC
14 points
23 comments1 min readLW link

How Not to be Stupid: Start­ing Up

Psy-Kosh28 Apr 2009 0:23 UTC
13 points
5 comments1 min readLW link

The Fal­lacy of Large Numbers

dspeyer12 Aug 2012 18:39 UTC
29 points
31 comments2 min readLW link

The Onion Goes In­side The Bi­ased Mind

patrissimo30 May 2009 17:33 UTC
8 points
3 comments1 min readLW link

Avoid­ing Failure: Fal­lacy Finding

Patrick3 Jul 2009 17:59 UTC
14 points
19 comments1 min readLW link

epistemic stal­ling.

Alfred10 Jan 2021 9:24 UTC
−2 points
18 comments1 min readLW link

The Par­tial Con­trol Fallacy

Darmani14 Dec 2016 2:57 UTC
28 points
2 comments2 min readLW link

The Case for Log­i­cal Fallacies

aaronb508 Mar 2021 3:04 UTC
12 points
0 comments7 min readLW link

Ir­ra­tional ar­gu­ments or valuable heuris­tics?

Hauntology Ph.D.8 Mar 2021 5:34 UTC
8 points
0 comments8 min readLW link
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