TagLast edit: 1 Oct 2020 22:45 UTC by Ruby

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
119 points
80 comments2 min readLW link

The Fal­lacy of Gray

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

Mind Pro­jec­tion Fallacy

Eliezer Yudkowsky11 Mar 2008 0:29 UTC
50 points
89 comments2 min readLW link

Catchy Fal­lacy Name Fal­lacy (and Sup­port­ing Disagree­ment)

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

The non­cen­tral fal­lacy—the worst ar­gu­ment in the world?

Scott Alexander27 Aug 2012 3:36 UTC
224 points
1,751 comments7 min readLW link

Plan­ning Fallacy

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

Fal­la­cies as weak Bayesian evidence

Kaj_Sotala18 Mar 2012 3:53 UTC
58 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
64 points
39 comments9 min readLW link

Con­junc­tion Fallacy

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

Car­diol­o­gists and Chi­nese Robbers

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

Prov­ing Too Much

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

Bur­den­some Details

Eliezer Yudkowsky20 Sep 2007 23:46 UTC
109 points
32 comments4 min readLW link

The Third Alternative

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

Your in­tu­itions are not magic

Kaj_Sotala10 Jun 2010 0:11 UTC
105 points
35 comments4 min readLW link

What cog­ni­tive bi­ases feel like from the inside

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

Talk­ing Snakes: A Cau­tion­ary Tale

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

The Log­i­cal Fal­lacy of Gen­er­al­iza­tion from Fic­tional Evidence

Eliezer Yudkowsky16 Oct 2007 3:57 UTC
70 points
58 comments6 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
43 points
36 comments6 min readLW link

The Haters Gonna Hate Fallacy

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

Pain is not the unit of Effort

alkjash24 Nov 2020 20:00 UTC
195 points
30 comments5 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
138 points
40 comments2 min readLW link

The Typ­i­cal Sex Life Fallacy

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

Make your train­ing useful

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

The Ep­silon Fallacy

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

The Pas­cal’s Wager Fal­lacy Fallacy

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

The Statis­ti­cian’s Fallacy

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

Dialogue on Ap­peals to Consequences

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

Hy­po­thet­i­cals: The Direct Ap­pli­ca­tion Fallacy

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

The Ge­netic Fallacy

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

Surely, rhetor­i­cal ques­tion?

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

The Sally-Anne fallacy

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

The Com­plete Idiot’s Guide to Ad Hominem

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

Three Fal­la­cies of Teleology

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

The Truth about Scots­men, or: Dis­solv­ing Fallacies

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

Flow­sheet Logic and Note­card Logic

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

Gen­er­al­iz­ing From One Example

Scott Alexander28 Apr 2009 22:00 UTC
320 points
412 comments6 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
67 points
42 comments4 min readLW link

Imag­i­nary Positions

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

The Fal­lacy of Dress­ing Like a Winner

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

Why *I* fail to act rationally

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

How Not to be Stupid: Start­ing Up

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

The Fal­lacy of Large Numbers

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

The Onion Goes In­side The Bi­ased Mind

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