READ Copi/Cohen, 8.2 & 8.3, pp. 261-272

8.4. THE FORMAL NATURE SYLLOGISTIC ARGUMENT

1. [Copi/Cohen, 274] Some introductory points: Copi/Cohen gives six rules governing validity in syllogisms. If ANY one of the rules is violated, then the argument is invalid. In some cases, arguments violate more than one rule--when this happens, the argument is not more invalid than if it had violated only one rule. The syllogistic rules concern the FORM of the argument, not its content; thus a violation of any of these rules is called a "formal" fallacy.

2. [Copi/Cohen, 274-5] The point of the first rule, as Copi/Cohen indicates, is to guarantee that the syllogism has three and only three terms. If one of the terms is ambiguous--a fairly common mistake--then the fallacy committed is called equivocation. A clear way for a termto be ambiguous is when different meanings seem to be intended in its two occurences in the syllogism. In such a case the term in the two statements is actually referring to two different classes. For example, when I say a person is a jewel, I mean it metaphorically; when I say the stone in my ring is a jewel, I mean it is a precious element (like emerald).

3. [Copi/Cohen, 276] To restate and summarize the point of rule #2: unless the middle term is distributed, i.e., refers to all the members of its class, then there is no certainty that the major and minor premisses have actually connected with each other through the middle term. The members of the classes referred to by the major and minor terms may differ; if so, then no conclusion has been validly established. Hence the rule that the middle term must be distributed in a valid categorical syllogism.

4. [Copi/Cohen, 276-7] The names of the fallacies described here usually take their more abbreviated form--i.e., "illicit major," "illicit minor."

5. [Copi/Cohen, 277] An alternative name for this fallacy is simply "two negatives," where it is understood that the fallacy consists in attempting to reason with two negative premisses. No valid conclusion can be drawn from this kind of reasoning.

6. In claiming an argument commits a fallacy you can either name the rule(s) broken, give the name of the formal fallacy, or do both.

INSTRUCTIONS: Do both sets of Exercises on 284-7 (Skip IV on p. 287). Some points:

(a) Read the Directions for these exercises very carefully: "Name the fallacies committed and the rules broken by any of the following syllogisms that are invalid." This does NOT say that all the syllogisms in the exercises are invalid; it says only that for those syllogisms which ARE invalid, you are asked to identify the fallacy and the rule broken.

(b) Review the "EXAMPLE" and "SOLUTION" on 285 for ideas on strategy to do the exercises.

(c) The syllogism in II are already in formal order, but those in III are not. Remember to go through the process with section III of identifying the conclusion, and hence the major and minor terms and premises, etc.