Tag Archives: Street-fighting logic

Re: Nonsense and Self-reports

Mr. Nance,

I am using your Introductory Logic course to teach an informal class in logic to four young people in my church. Thank you for creating a rigorous, explicitly-Christian logic textbook!

During a recent class (working through Lessons 6-8), two questions came up. Can I get your thoughts on them?

(1) Nonsense Statements

On page 57 you give the example of the nonsense sentence “The round square sweetly kicked the green yesterday.” A few students began waxing philosophical about what precisely rendered this sentence nonsense. One asked if it was nonsense in virtue of the fact that squares, by definition, cannot be round. If so, they asked, wouldn’t the sentence, “The square sweetly kicked the green yesterday” be eligible for statement-hood? Sure, squares aren’t known to kick, but that only means that the sentence is likely a false statement. Further, “green” might refer metaphorically to the green grass or a public common grassy land.

I love having such inquisitive students, but I’m afraid I wasn’t able to give them a tidy answer to these questions: Instead, I suggested that we take statements like “this statement is false” as clear examples of nonsense and leave the rest for an epistemology class. What would you have said?

(2) Self-supporting statements

There was some consternation about the notion that self-supporting statements are true (p. 61). One student gave the example of James 2:14 where the self-report “I have faith” is false. I answered by saying that, in general, we should give self-reports the benefit of the doubt. That is, we should judge a self-report true, until or unless we have some good reasons or arguments for thinking it false. Of course, this doesn’t mean that all self-reports are true. Categorizing self-reports as self-supporting, I told them, is more a point of intellectual decency and doing-as-you-would-be-done by than of hard logical categories.

I also pointed out that many self-reports fall into the category of incorrigible statements—that is, for some self-reports, we simply will never have any means, whether by authority, experience, or deduction, of proving them false. Most self-reports about mental states fall into this category—for example, “I wish I had purchased Apple Stock five years ago.”

If you can give any general pointers here, I would be grateful. Thank you. Continue reading Re: Nonsense and Self-reports

Fallacies in Comics

Comic strips are a great place to find examples of informal fallacies. It seems that we tend to find improper reasoning funny. In the “Peanuts” comic strip below, Lucy is ad baculum incarnate.


Note that the fallacy is not really made by Lucy making the threat, but by Charlie Brown, who is convinced by her “argument.”

Here is another example, where Lucy persuades Linus to memorize his lines using “five good reasons”: Continue reading Fallacies in Comics

Analyzing a real argument

Mr. Nance,

I lead a group of young men in Intermediate Logic and they wanted to put their skills to use. They used an argument they pulled from chapter 1 of the book Defeating Darwinism. We tried several different ways of representing the propositions but always came up with an invalid argument. We really want it to be valid! What do we need to do? The original argument is: “If God created space and time, then He is outside of time. Therefore, He is not affected by time.” Any helpful hints will be very appreciated. Continue reading Analyzing a real argument