Four-term fallacy
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A four-term fallacy (also quaternio terminorum, fallacy of four terms, and if using equivocation, ambiguous middle term) occurs when a syllogism uses four or more terms instead of the required three.
The fallacy is a formal fallacy, because the conclusion does not follow even if the premises are correct.
Contents
Form[edit]
A four term fallacy uses (at least) four terms, represented here as letters W, X, Y, and Z. The fallacy (when limited to 4 terms) takes two forms. First, where the premises contain 4 terms:
P1: W is X.
P2: Y is Z.
C1: W is Z.
Second, where a new term is introduced in the conclusion:
P1: X is Y.
P2: Y is Z.
C1: W is X.
In both cases, the conclusion does not follow, because all of the terms used in the conclusion are not used in the premises. Compare this to a proper syllogism:
P1: X is Y.
P2: Y is Z.
C1: X is Z.
Here, only three terms (X, Y, and Z) are used, and both terms used in the conclusion are used in the premises.
Examples[edit]
Using the first form:
Using the second form:
- P1: All fish have fins.
- P2: All goldfish are fish.
- C1: All humans have fins.
Many first-cause arguments are based on a four-term fallacy:
- P1: All events have a cause.
- P2: Causal chains have to start somewhere.
- C1: God is the cause!
Wow, that God really came out of nowhere! *ba-dum-tss*
See also[edit]
Equivocation, one of the most common four-term fallacies
External links[edit]
- See the Wikipedia article on Fallacy of four terms.
- FALLACY OF FOUR TERMS, Logically Fallacious