Category Archives: Ask-a-question

An Enthymeme of P. J. O’Rourke

Mr. Nance,

I have a question about enthymemes. When the conclusion is assumed, how do we know which is the major premise and which is the minor premise? I fear there is a simple explanation that I may have missed but when I compare your example in Introductory Logic on page 221 with Exercise 31 #5, I can’t correlate how you knew which was the major premise and which was the minor premise, and therefore, how to write the assumed conclusion in proper form. Continue reading An Enthymeme of P. J. O’Rourke →

Predicate noun in categorical form

Mr. Nance,

One question on 6A, problem #11. My son struggles getting a nominative in the predicate consistently. His current method is to repeat the subject (e.g. No bats are blind bats), which I tell him isn’t allowed (based on example), but he requests a better reason than that. (It being circular didn’t impress him, either.) Help? Continue reading Predicate noun in categorical form →

More than a switching

Mr. Nance,

Tomorrow morning I will be explaining why EIO-2 is valid but IEO-2 is invalid. The only problem is that I think both ought to be valid. I do not understand why reversing the order of the premises invalidates the syllogism, especially when the placement of the middle term remains the same. Thank you in advance. Continue reading More than a switching →

Fixing a counterexample

Mr. Nance,

One of my students came up with a counter-example for OAO-1 (#6 Quiz 9) in class yesterday:

Some fish are not cats.
All catfish are fish.
∴ Some catfish are not cats.

Because of subimplication “NO catfish are cats” is true, would this counterexample be incorrect since “some catfish are not cats” is implied to be true as well? We had several class examples so by the end of the class, we were all a bit bogged down.

Thanks for your help! Continue reading Fixing a counterexample →

A real-life enthymeme

Mr. Nance,

An article included said of the following argument, “That’s a syllogism without a minor premise”:

“[P]olitical decisions in the modern world often concern how to deploy science and technology, so people well-trained in science and technology will be better prepared to make those decisions.”

I would like to give this to my students to work on, but I can’t seem to translate Jacob’s rendering into terms that work formally. Do you have time to take a look?

All the Best. Continue reading A real-life enthymeme →

Categorical form & getting the subject right

Mr. Nance,

In the Introductory Logic video Lesson 12, you write this sentence on the white board: “Some days the sun just doesn’t shine.” The first rule to put this sentence into the proper form states: Identify and write the complete subject. You identified “days” as the subject. Essentials taught me to ask, “Who or what does (not) shine?” Doesn’t that mean that “the sun” is the subject? How imperative is it that the subject be identified correctly?  Continue reading Categorical form & getting the subject right →

The One Basic Verb & Past Tense

Mr. Nance,

In the Intro Logic course, the answer guide shows that a past tense statement, “God created heaven and earth”  was converted to the present tense, “God is the Creator of heaven and earth.” I clearly see that the subject of the sentence (God) is like no other subject…is that why? Or would you have done this with a similar sentence? “Jane Austen authored Pride and Prejudice.” –> “Jane Austen is the author of Pride and Prejudice.” (I am wondering if you have an exception to the Caution printed on the previous page.) Thank you!

Continue reading The One Basic Verb & Past Tense →