Exercise: The following will give the student good practice and exercise in the methods of Conversion. It affords a valuable mental drill, and tends to develop the logical faculties, particularly that of Judgment. The student should convert the following propositions, according to the rules and examples given in this chapter:
1. All men are reasoning beings.
2. Some men are blacksmiths.
3. No men are quadrupeds.
4. Some birds are sparrows.
5. Some horses are vicious.
6. No brute is rational.
7. Some men are not sane.
8. All biscuit is bread.
9. Some bread is biscuit.
10. Not all bread is biscuit.
CHAPTER XIII.
REASONING
In the preceding chapters we have seen that in the group of mental processes involved in the general process of Understanding, there are several stages or steps, three of which we have considered in turn, namely: (1) Abstraction; (2) Generalization or Conception; (3) Judgment. The fourth step, or stage, and the one which we are now about to consider, is that called Reasoning.
Reasoning is that faculty of the mind whereby we compare two Judgments, one with the other, and from which comparison we are enabled to form a third judgment. It is a form of indirect or mediate comparison, whereas, the ordinary Judgment is a form of immediate or direct comparison. As, when we form a Judgment, we compare two concepts and decide upon their agreement or difference; so in Reasoning we compare two Judgments and from the comparison we draw or produce a new Judgment. Thus, we may reason that the particular dog "Carlo" is an animal, by the following process:
(1) All dogs are animals; (2) Carlo is a dog; therefore, (3) Carlo is an animal. Or, in the same way, we may reason that a whale is not a fish, as follows:
(1) All fish are cold-blooded animals; (2) A whale is not a cold-blooded animal; therefore, (3) A whale is not a fish.