Illicit Conversion
Alias: False ConversionType: Fallacy of Quantificational Logic
| Forms | |
|---|---|
| All P are Q.
Therefore, all Q are P. |
Some P are not Q.
Therefore, some Q are not P. |
| Similar Validating Forms | |
| No P are Q.
Therefore, no Q are P. |
Some P are Q.
Therefore, some Q are P. |
| Examples | |
| All communists are atheists.
Therefore, all atheists are communists. |
Some dogs are not pets.
Therefore, some pets are not dogs. |
| Counter-Examples | |
| All dogs are mammals.
Therefore, all mammals are dogs. |
Some mammals are not cats.
Therefore, some cats are not mammals. |
Exposition:
Conversion is a validating form of immediate inference for E- and I-type categorical propositions. To convert such a proposition is to switch the subject and predicate terms of the proposition, which is non-validating for the A- and O-type propositions. Hence, the fallacy of Illicit Conversion is converting an A- or O-type proposition.
Source:
Paul Edwards (Editor in Chief), The Encyclopedia of Philosophy, (Macmillan, 1972), Volume 3, pp. 170-1.
