Fallacies of Ambiguity
Fallacies of ambiguity arise from ambiguities or vagueness in language.
1. Equivocation
In equivocation, a word or term is used with different meanings as if it had the same meaning.
Example:
- Equivocation in the middle term of a syllogism
In English and in French, the same word does duty for "man" and "human being". That yields strange arguments like this one.
Only man has rights. (man = humain)
Women are not men\ (men = male humain) Hence, women has no rights.
Since the middle term ("man") is used equivocally here, the inference becomes incorrect and its conclusion nonsense. (The inference is merely a quaternio terminorum / non sequitur.)
It works exactly the same way in French, because "homme" means both "human being" and "man":
Seul l'homme a des droits. (homme = être humain)
Les femmes ne sont pas des hommes. (hommes = humains de sexe masculin)
Donc, les femmes n'ont pas de droits.
Why is this flawed? The word "man" is first used in the sense of "human being", then it is implicitly switched to "male human being".
2. Amphiboly
Amphiboly arises from grammatical ambiguity that can lead to different interpretations.
Examples:
- The Oracle of Delphi (classic)
If you cross the river Halys, you will destroy a great empire.
What is unclear is which empire: the enemy's or his own. Croesus read it as a promise of victory, crossed the river and destroyed his own empire. This is the textbook example of amphiboly from antiquity, and at the same time it shows how ambiguity can be exploited in argument.
- Prepositional attachment ("with the …")
"The police chased the thief with the motorbike."
Reading A: the police used the motorbike.
Reading B: the thief was on the motorbike.
The ambiguity arises purely from the position of the prepositional phrase, not from an ambiguous word. (Variant: "He watched the woman with the binoculars.")
- Genitive: subject or object?
The fear of the enemies was great.
Reading A: the enemies were afraid (genitivus subjectivus).
Reading B: people were afraid of the enemies (genitivus objectivus).
The same construction produces the same ambiguity in "the love of God" or "the criticism of the students": who is criticising whom?
3. Accent
This fallacy arises from incorrect stress or emphasis that changes the meaning of a statement.
Example: "We should not speak badly about our colleagues." (Depending on which word is stressed, the meaning changes.)
4. Composition
In the fallacy of composition, it is wrongly assumed that a property of the parts must also be a property of the whole.
Example: "Every part of this computer is light. Therefore the computer is light."
Why is this flawed? The property "light" of the individual parts does not necessarily transfer to the whole.
Brain example "The neurons are not visible to the naked eye, so the brain is not visible to the naked eye."
5. Division
The fallacy of division is the opposite of the fallacy of composition: it is wrongly assumed that a property of the whole must also be a property of each part.
Example: "Germany is a rich country. Therefore every German is rich."
Why is this flawed? The property "rich" of the country as a whole does not necessarily transfer to each individual citizen.
Brain example "The brain can think, so the neurons can think."