1423:
90:
Notice that there are four terms: "weapon", "dangerous", "balloon", and "round". The two premises do not connect "balloons" with "dangerous", so the reasoning is invalid. Two premises are not enough to connect four different terms, since in order to establish connection, there must be one term
220:
is a frequently cited source of a fourth term being added to a syllogism; both of the equivocation examples above affect the middle term of the syllogism. Consequently this common error itself has been given its own name: the fallacy of the ambiguous middle. An argument that commits the ambiguous
112:
The word "nothing" in the example above has two meanings, as presented: "nothing is better" means the thing being named has the highest value possible (there exists nothing better); "better than nothing" means only that the thing being described has some value (more than the implied zero value of
98:: using the same word or phrase but with a different meaning each time, creating a fourth term even though only three distinct words are used. The resulting argument sounds like the (valid) first example above, but is in fact structured like the invalid second example:
124:
Sometimes a syllogism that is apparently fallacious because it is stated with more than three terms can be translated into an equivalent, valid three term syllogism. For example:
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nothing). Therefore, "nothing" acts as two different terms in this example, thus creating the fallacy of four terms.
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178:(that is, the statement "No humans are immortal." is equivalent to the statement "All humans are mortal.").
225:
fallacies, however it is usually considered an informal fallacy because the argument's form appears valid.
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syllogism by first substituting the synonymous term "humans" for "people" and then by reducing the
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24:
1441:
1178:
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203:
116:
The fallacy of four terms also applies to syllogisms that contain five or six terms.
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609:
213:
95:
313:
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40:
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36:
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94:
In everyday reasoning, the fallacy of four terms occurs most frequently by
400:
1278:
202:, all of which must have exactly three terms. Because it applies to the
432:
159:
155:
151:
143:
16:
Formal fallacy that occurs when a syllogism has four (or more) terms
404:
69:
Here, the three terms are: "weapon", "dangerous", and "knife".
206:, as opposed to the argument's content, it is classified as a
108:
Conclusion: A ham sandwich is better than eternal happiness.
102:
Major premise: Nothing is better than eternal happiness.
105:
Minor premise: A ham sandwich is better than nothing.
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761:
733:
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531:
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453:
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347:
324:
221:middle fallacy blurs the line between formal and
190:. Types of syllogism to which it applies include
383:Fallacy of the Four Terms (quaternio terminorum)
379:Understanding Defectice Arguments, thoughtco.com
55:Categorical syllogisms always have three terms:
170:term "immortal" in the first premise using the
541:Affirmative conclusion from a negative premise
162:". But it can be rewritten as a standard form
43:rather than the requisite three, rendering it
546:Negative conclusion from affirmative premises
416:
8:
377:How Logical Fallacy Invalidates Any Argument
1274:
1121:
996:
599:
450:
423:
409:
401:
282:
258:
246:
239:
318:. Vol. 1. Longmans, Green and Co.
294:
142:syllogism apparently has five terms: "
128:Major premise: No humans are immortal.
346:Copi, Irving M.; Cohen, Carl (1990).
270:
131:Minor premise: All Greeks are people.
80:Major premise: Weapons are dangerous.
59:Major premise: Weapons are dangerous.
7:
86:Conclusion: Balloons are dangerous.
134:Conclusion: All Greeks are mortal.
83:Minor premise: Balloons are round.
62:Minor premise: Knives are weapons.
14:
65:Conclusion: Knives are dangerous.
1422:
1421:
331:. University Press of America.
186:The fallacy of four terms is a
919:Correlation implies causation
1:
91:common to both premises.
354:(8th ed.). Macmillan.
1464:
1343:I'm entitled to my opinion
1417:
1326:
1199:
1369:Motte-and-bailey fallacy
469:Affirming the consequent
1389:Two wrongs make a right
720:Denying the correlative
1374:Psychologist's fallacy
1311:Argument to moderation
1301:Argument from anecdote
1251:Chronological snobbery
875:Quoting out of context
842:Overwhelming exception
725:Suppressed correlative
625:Quoting out of context
500:quantificational logic
474:Denying the antecedent
323:Cogan, Robert (1998).
312:Coffey, Peter (1912).
196:hypothetical syllogism
28:
1448:Syllogistic fallacies
1337:The Four Great Errors
1317:Argumentum ad populum
1306:Argument from silence
1010:Argumentum ad baculum
788:Faulty generalization
479:Argument from fallacy
395:Ambiguous Middle Term
389:The Four Term Fallacy
350:Introduction to Logic
283:Copi & Cohen 1990
259:Copi & Cohen 1990
247:Copi & Cohen 1990
200:categorical syllogism
192:statistical syllogism
21:fallacy of four terms
1355:Invincible ignorance
1161:Reductio ad Stalinum
1147:Reductio ad Hitlerum
1103:Wisdom of repugnance
870:Moving the goalposts
735:Illicit transference
660:Begging the question
581:Undistributed middle
489:Mathematical fallacy
464:Affirming a disjunct
315:The Science of Logic
29:quaternio terminorum
1088:Parade of horribles
1064:In-group favoritism
890:Syntactic ambiguity
533:Syllogistic fallacy
456:propositional logic
297:, pp. 302–304.
261:, pp. 214–217.
249:, pp. 206–207.
223:informal (material)
188:syllogistic fallacy
172:immediate inference
39:has four (or more)
35:that occurs when a
1174:Poisoning the well
991:Proof by assertion
966:Texas sharpshooter
900:Questionable cause
837:Slothful induction
796:Anecdotal evidence
656:Circular reasoning
551:Exclusive premises
513:Illicit conversion
397:, fallacyfiles.org
391:, fallacyfiles.org
1435:
1434:
1413:
1412:
1409:
1408:
1349:Ignoratio elenchi
1261:
1260:
1111:
1110:
1073:Not invented here
778:Converse accident
700:Correlative-based
677:Compound question
620:False attribution
615:False equivalence
589:
588:
385:, onegoodmove.org
361:978-0-02-325035-4
338:978-0-7618-1067-4
327:Critical Thinking
273:, pp. 95–96.
72:Using four terms
1455:
1425:
1424:
1396:Special pleading
1275:
1136:Appeal to motive
1122:
1098:Stirring symbols
1078:Island mentality
1016:Wishful thinking
997:
713:Perfect solution
690:No true Scotsman
685:Complex question
670:Leading question
649:Question-begging
635:No true Scotsman
600:
523:Quantifier shift
518:Proof by example
451:
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1379:Rationalization
1322:
1269:
1257:
1195:
1117:Genetic fallacy
1107:
1020:
995:
970:
894:
885:Sorites paradox
865:False precision
846:
827:Double counting
782:
757:
729:
694:
681:Loaded question
665:Loaded language
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204:argument's form
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76:the syllogism:
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12:
11:
5:
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1209:Accomplishment
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993:
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961:Slippery slope
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880:Slippery slope
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806:Cherry picking
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371:External links
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287:
285:, p. 206.
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208:formal fallacy
183:
182:Classification
180:
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121:
120:Reducing terms
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110:
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106:
103:
88:
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67:
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52:
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33:formal fallacy
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1069:Invented here
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832:False analogy
830:
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801:Sampling bias
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764:Secundum quid
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709:
708:False dilemma
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607:
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601:
598:
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582:
579:
577:
576:Illicit minor
574:
572:
571:Illicit major
569:
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168:complementary
165:
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34:
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26:
22:
1364:Naturalistic
1347:
1335:
1315:
1286:
1270:of relevance
1213:
1191:Whataboutism
1183:
1159:
1153:Godwin's law
1145:
1125:
1008:
1001:Consequences
982:Law/Legality
956:Single cause
929:
922:
762:
630:Loki's Wager
610:Equivocation
603:Equivocation
565:
349:
326:
314:
290:
278:
266:
254:
242:
214:Equivocation
212:
185:
137:
123:
115:
111:
96:equivocation
93:
89:
71:
68:
54:
20:
18:
1384:Red herring
1141:Association
822:Conjunction
743:Composition
640:Reification
556:Existential
508:Existential
295:Coffey 1912
218:middle term
74:invalidates
1360:Moralistic
1294:Sealioning
1288:Ad nauseam
1215:Ipse dixit
1127:Ad hominem
951:Regression
753:Ecological
566:Four terms
484:Masked man
271:Cogan 1998
229:References
51:Definition
1401:Straw man
1279:Arguments
1268:fallacies
1242:Tradition
1232:Etymology
1204:Authority
1185:Tu quoque
1169:Bulverism
939:Gambler's
908:Animistic
852:Ambiguity
818:Base rate
561:Necessity
433:fallacies
176:obversion
174:known as
37:syllogism
31:) is the
1442:Category
1427:Category
1059:Ridicule
1044:Flattery
1034:Children
931:Post hoc
811:McNamara
773:Accident
748:Division
595:Informal
158:", and "
148:immortal
1246:Novelty
1221:Poverty
1083:Loyalty
1049:Novelty
1026:Emotion
975:Appeals
944:Inverse
924:Cum hoc
913:Furtive
431:Common
216:of the
45:invalid
1331:Cliché
1266:Other
1237:Nature
1225:Wealth
860:Accent
446:Formal
358:
335:
198:, and
160:mortal
156:people
152:Greeks
144:humans
1093:Spite
987:Stone
305:Books
234:Notes
164:AAA-1
140:EAE-1
138:This
41:terms
25:Latin
1179:Tone
1054:Pity
1039:Fear
437:list
356:ISBN
333:ISBN
154:", "
150:", "
146:", "
19:The
498:In
454:In
1444::
1362:/
1244:/
1223:/
1071:/
989:/
820:/
683:/
679:/
658:/
210:.
194:,
47:.
27::
439:)
435:(
424:e
417:t
410:v
364:.
341:.
23:(
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.