The material fallacies are fallacies of meaning and not of form. They are those arising from inconsistency in thought, and from imperfect ways of interpreting this thought as it appears in language. No very specific rules of logic are violated by them and for this reason there are those who would entirely eliminate the material fallacies from the field of logic. But since thought is even more subtle than form in its deceitful machinations, we believe that the material fallacy calls for special attention on the part of the logician.
Material fallacies are divided into two kinds. First, those which have reference to wrong thinking, or fallacies in thought; and, second, those which are due mainlyto an incorrect interpretation of words, or fallacies in language. The former result from inconsistency and unreasonableness in thought, whereas the latter come from lack of precision in expression.
5. FALLACIES OF IMMEDIATE INFERENCE.
Fallacies of immediate inference arise from some violation of the rules which this topic enunciates.
(1) Opposition.
Among other statements opposition posits these two: (1) When the particular is true its opposing universal is indeterminate; (2) A universal negative does not necessarily contradict a universal affirmative.
These signify that neither an A nor an E must be assumed to be true when the corresponding I or O is true, and that E may not always contradict A, nor O contradict I.
ILLUSTRATIONS OF FALLACIES OF OPPOSITION.
(1) Since some men are wise, then I may conclude that all men are wise.
(2) I have contradicted his statement “all men are honest” by proving that no men are honest.