=21. QUESTIONS FOR ORIGINAL THOUGHT AND INVESTIGATION.= (1) May both premises of a hypothetical argument be hypothetical propositions? Explain. See Fowler p. 115. (2) Which of the two is valid? Explain. (1) If A is B, C is D If A is B, E is F ∴ If C is D, E is F (2) If A is B, C is D If C is D, E is F ∴ If A is B, E is F (3) Show by circles that two of the possible four hypothetical arguments are invalid. (4) What categorical rules does the hypothetical argument seem to violate? Explain. (5) Originate a hypothetical syllogism whose antecedent and consequent are both negative. Test its validity. (6) Originate a co-extensive hypothetical argument and show that four valid syllogisms may be derived from it. (7) Explain by word and illustration the two meanings which may be attached to “either-or.” (8) If we accepted the opinion that both alternates of a disjunctive may be true, which kind of disjunctive argument would it invalidate? (9) In a logical disjunction what law of thought is involved? Explain. (10) Why do the laws of the disjunctive seem to contradict the categorical rules? Explain fully. (11) Show by drawing on common experience that a logical dilemma is closely related to the popular conception of dilemma. (12) Illustrate by symbols and then place in good English a pentalemma. (13) State a definition of a dilemma which excludes the simple destructive form. (14) Give a common experience which, when thrown into argumentative form, results in a disjunctive proposition followed by a hypothetical syllogism. Coin a name for such a combination. CHAPTER 16. THE LOGICAL FALLACIES OF DEDUCTIVE REASONING. =1. A NEGATIVE ASPECT.= It has been remarked that “Logic as a science makes known the laws and forms of thought and as an art suggests conditions which must be fulfilled to think rightly.” In recent chapters we have discussed the second aspect of the definition; in these we have attempted to answer the question, “What _rules_ must be followed in order to reason correctly?” We are now ready to treat the same aspect from a negative point of view namely, what _errors_ must be avoided in order to reason correctly? What are the fallacies which we must strive to avoid in our _own_ thinking, and attempt to correct in the thinking of _others_? =2. PARALOGISM AND SOPHISM.=