Intensional fallacy
The intentional fallacy is a fallacy based on the fact that the expressions of the premises are replaced by expressions with the same reference, although there is a context in which this can lead to deviations in the verifications, a so-called intensional context .
The intentional fallacy must be distinguished from the intentional fallacy . One is about the intention (meaning), the other is about the intention (intention).
A classic example of an intensional fallacy:
- The evening star is identical to the morning star (the star / planet Venus).
- Mike knows that the evening star is the first star / planet to be visible in the evening.
- So: Mike knows that the morning star is first visible in the evening sky.
Even if the terms “evening star” and “morning star” denote the same thing, in intensional contexts one term cannot simply be replaced by another extension-like one. Because if Mike does not know premise 1. and only 2., he does not yet know 3.
The fallacy can lead to errors in both directions:
- Either one can infer that if a person knows, believes etc. something about x, he knows, believes etc. the same about the extension-identical expression y.
- Or one incorrectly concludes that expressions with the same extension cannot be involved if a person knows something about x but not about the expression y, whose extension equality is in question.
Another, intercultural example is the use of the expression "God":
- 1. “God” in German denotes the same “object” as “Deus” in Latin or as “Allah” in Arabic.
- 2. Müller believes in God.
- 3. So: Müller also believes in Allah.
- 3 '. or: if conclusion 3. does not apply, premise 1. cannot apply.
literature
- Peter Prechtl: Wrong conclusion, more intensional. In: P. Prechtl (ed.): Basic concepts of analytic philosophy. Metzler, Stuttgart a. a. 2004.
- Holm Tetens : Philosophical Argumentation. Beck, Munich 2004, p. 126 f.