(b) Original: Some men are not wise. Converted: (incorrectly) Some wise beings are not men.
(4) Contraversion.
As this process involves the two steps of obversion and conversion, fallacies appertaining to contraversion would relate to these two steps.
ILLUSTRATIONS OF FALLACIES OF CONTRAVERSION.
(a) Original: No honest man fails to pay his debts. Contraverted: (incorrectly) Some who do not pay their debts are honest men.
(b) Original: Some animals are quadrupeds. Contraverted: (incorrectly) Some not-quadrupeds are not animals.
The formal fallacies of categorical, hypothetical, and disjunctive arguments have received detailed treatment inchapters 11, 14 and 15; we may, therefore, devote our attention to the material fallacies without further delay.
6. FALLACIES OF LANGUAGE. (Equivocation.)
These are the fallacies of double meaning. It is known that an equivocal term is one which permits two or more interpretations; similarly a proposition which admits of two or more interpretations may be denominated equivocal. Thus the term equivocation has come to stand for all errors in language resulting from a possibility of more than one interpretation. This justifies the position of referring to all of the six fallacies in language as fallacies also of equivocation.
(1) Ambiguous middle.