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Affirmative conclusion from a negative premise
From Wikipedia, the free encyclopedia
Affirmative conclusion from a negative premise is a logical fallacy that is committed when a categorical syllogism has a positive conclusion, but one or two negative premises.
For example:
- No fish are dogs, and no dogs can fly, therefore all fish can fly.
This could be illustrated mathematically as
- If A ⊄ B and B ⊄ C then A ⊂ C.
It is a fallacy because any valid forms of categorical syllogism that assert a negative premise must have a negative conclusion.
| Argument from fallacy | Fallacy of modal logic | Masked man fallacy | Appeal to probability
|
|
|---|---|
| Fallacy of propositional logic: | |
| Affirming a disjunct | Affirming the consequent | Commutation of Conditionals Denying a conjunct | Denying the antecedent | Improper Transition |
|
| Fallacy of quantificational logic: | |
| Existential fallacy | Illicit Conversion | Quantifier shift | Unwarranted contrast | |
| Syllogistic fallacy: | |
| Affirmative conclusion from a negative premise | Negative conclusion from an affirmative premise Exclusive premisses | Necessity | Four-term Fallacy | Illicit major | Illicit minor | Undistributed middle |
|
| Other types of fallacy | |
