3. A DIVISION OF THE DEDUCTIVE FALLACIES.
The mistakes of induction will occupy our attention in a later chapter. We are now concerned with the fallacies of deduction. Any classification or division of the deductive fallacies must of necessity be faulty. Even the labors of Aristotle in this regard are now pronounced crude and unsatisfactory. This is due to the divergence of opinion as to the signification of some of the fallacies, as well as to the fact that no division is free from the fault of an overlapping of the species. As a result of this lack of unanimity in definition and lack of ability in making the species mutually exclusive, any division of the deductive fallacies must be more or less illogical.
Aristotle divides the fallacies of deduction into two groups: (1) Fallacies in dictione, or formal fallacies. (2) Fallacies extra dictionem, or material fallacies. This division has received universal approval and though many distinctions made by him have been abandoned, yet most logicians retain his phraseology. Since many of the technicalterms which Aristotle used have lived through the generations under the conventional meaning which he assigned to them, it becomes less confusing to adhere as closely as possible to these terms. Therefore, in the attending division only those changes have been made which progress and experience have forced upon us. What remains of this chapter will be devoted to explaining these fallacies as they appear in this division. For the sake of clearness and definiteness it is strongly recommended that the student study the outline extensively enough to be able to reproduce it.
| Formal (In dictione) | ||
|---|---|---|
| 1. Immediate inference |  | 1. Opposition |
| 2. Obversion | ||
| 3. Conversion | ||
| 4. Contraversion | ||
| 2. Categorical arguments | | 5. Four terms |
| 6. Undistributed middle | ||
| 7. Illicit major | ||
| 8. Illicit minor | ||
| 9. Negative premises | ||
| 10. Particular premises | ||
| 3. Hypothetical arguments | | 11. Denying the antecedent |
| 12. Affirming the consequent | ||
| 4. Disjunctive arguments | | 13. Illogical disjunction |
| Material (In dictionem) | ||
| 1. In Language Equivocation | | 1. Ambiguous middle |
| 2. Amphibology | ||
| 3. Accent | ||
| 4. Composition | ||
| 5. Division | ||
| 6. Figure of speech | ||
| 2. In Thought Assumption | | 1. Accident |
| 2. Converse accident | ||
| 3. Irrelevant conclusion | ||
| 4. Non sequitur | ||
| 5. False cause | ||
| 6. Complex question | ||
| 7. Begging the question | ||