Rhetoric Lesson 5 Logic Review

[Henle Redneck]

Could you explain how you constructed the first syllogism on p.36? I cannot figure out how to work the phrases that Aristotle gives into valid, proper enthymemes, nor can I get what the teacher key has. I am even more confused when I look at the answer key for the second and third syllogisms. I could not find Exercise 5-2 in Chapter 6 of Traditional Logic Book II which was referred to on p.36 of the Rhetoric book.

[martin]

The first statement runs like this: “We must also notice the ends which the various forms of government pursue, since people choose in practice such actions as will lead to the realization of their ends.”

As I explain in Traditional Logic II, in order to reconstruct a full argument from an enthymeme (which is an argument missing one of its statements, as we have here), we have to first identify the conclusion. What is the part of the statement that the other statement supports, the main assertion? Often it is the first statement and then the premise follows (usually signaled by a word like “since,” “because,” or “for.”

In this case, the first statement is clearly the conclusion:

We must also notice the ends which the various forms of government pursue.

If the statement isn’t in clear logical form, then we have to put it in something like logical form. That means we have to have a clear quantifier, subject, copula, and predicate. We don’t have that here, so let’s do that. In order to determine the qualifier, we must ask the statement’s quantity and quality. Is affirmative or negative? Universal or particular? The author here seems to be making a universal statement, in which case the quantifier should be “All” or “No,” depending on whether it is affirmative or negative. It is clearly affirmative, so it must be “all.”

The subject is the thing the statement is about. This statement is about the ends of various forms of government, so that must be the subject “the ends of various forms of government.”

The predicate is what is being said about the subject. In this case what is being said about the subject is that it must be noticed.

The copula will fall into place when we construct the statement, which we will do now:
All ends of various forms of government are things that must be noticed.

Now we want to add the premise, which is the statement that follows the “since” in the quote above: “people choose in practice such actions as will lead to the realization of their ends.” We just follow the same procedure:

All (it is a universal/affirmative) ends which various forms of government pursue (one of the elements of the conclusion above must be in this statement, and this one is the obvious one) are (copula) actions (this is the complement we provide in order to make it sound right) which will lead to the realization of people’s ends (this is the predicate pretty much straight from the statement).

So we have:

All ends which various forms of government purse are actions which will lead to the
realization of peoples’ ends

All ends of various forms of government are things that must be noticed

So we have to provide the missing premise. Let’s first decide which premise is missing, the major or minor. If the given premise has the major term, then we are missing the minor premise; if the given premise has the minor term, then we are missing the major premise. The given premise has the minor term (the subject of the conclusion), therefore we are missing the major premise.

The major premise must be Barbara, since both the minor premise and the conclusion begin with “All,” and the only valid syllogism of the possible 19 valid syllogisms in the mnemonic verse that have an A minor premise and an A conclusion is Barbara. Therefore, we know that the missing premise is an A statement.

In a Barbara, the major premise has the middle term in the subject and the major term in the predicate. The middle term here is “things that will lead to the realization of peoples’ ends,” since that is the only term that is not in the conclusion. And the major term is “things that must be noticed” (since that is the predicate of the conclusion). So the missing premise is “All things that will lead to the realization of people’s ends are things that must be noticed.”

All things that will lead to the realization of people’s ends are things that must be
noticed.
All ends which various forms of government purse are actions which will lead to the
realization of peoples’ ends
All ends of various forms of government are things that must be noticed

Just try this procedure out on the other statements as well and let me know how you do.