4. GENERAL DIVISIONS EXPLAINED.
The formal fallacies are those which concern the form of the argument rather than the meaning.These fallacies arise from an improper use of words as arbitrary signs of thought, not from any inconsistency in the thought itself. To commit a formal fallacy we must violate one of the specific rules of logic. For this reason the formal fallacies are easier of comprehension. Moreover, because of this definiteness logicians are better able to come to some agreement as to their content and import. Classing the fallacies of immediate inference as formal is somewhat of an innovation; but since they occur because of the breaking of certain definite rules, and since immediate inference is a matter of changing the form without altering the meaning, we believe there is some justification for this position. Some would class “immediate inference” fallacies with the material fallacies of language.
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.