# An Interesting Logic Textbook

Jeffrey Shallit has an interesting post up about The Southern Confederacy Arithmetic, a mathematics textbook published in 1864. Some of its idiosyncratic examples make for amusing reading.

Reading Jeffrey’s post reminded me of a textbook I picked up at home-schoolers convention a while back. The book is called Intermediate Logic For Christian and Home Schools, by James Nance. Now, I am happy to report that the logic presented in the book is the same logic you would find in any other textbook. It covers all the standard banalities of basic propositional logic, and does so in an entirely competent way. But some of the examples certainly cause a raised eyebrow.

The back cover contains a description of the book, which begins like this.

Logic is the art of reasoning well–of learning to think God’s thoughts after Him.

The theme continues in the book’s introduction:

Logic has been defined both as the science and the art of correct reasoning. People who study different sciences observe a variety of things; biologists observe living organisms, astronomers observe the heavens, and so on. From their observations they seek to discover natural laws by which God governs His creation. The person who studies logic as a science observes the mind as it reasons–as it draws conclusions from premises–and fro those observations discovers laws of reasoning which God has placed in the minds of people.

Textbooks of this sort are endlessly reminding you of God’s role in things. In this case, though, the atheist part of me had to smirk a bit more than usual. After all, for many people learning about logic and critical thinking is the first step away from belief in God.

But it’s the examples that are especially striking. For instance, the opening section of the book introduces the idea of a “proposition.” The section concludes with a sequence of exercises. One of them provides a list of statements, next to which the letters S and C appear. The instructions direct the student to circle S or C according to whether the given proposition is simple or compound. Here are the propositions:

• The Lord will cause your enemies to be defeated before your eyes.
• There is a way that seems right to a man but in the end it leads to death.
• The fear of the Lord is the beginning of wisdom.
• If we confess our sins then He is faithful to forgive us our sins.
• It is false that a good tree bears bad fruit and that a bad tree bears good fruit.
• The Kingdom of God is not a matter of talk but of power.

Later the notion of a valid argument is introduced. The student is instructed to translate certain arguments into symbols, and then determine whether or not they are valid. Here is one of the examples:

If Jesus is not God then He was a liar or He was insane. Jesus was clearly not a liar. He certainly was not insane. We conclude that Jesus is God.

I’d say that’s a good example of an argument that’s valid but not sound.

And then there’s this one:

If evolutionary theory is correct then the biblical creation account is false. However, if the Bible is God’s word then the biblical creation account is true. Therefore if evolutionary theory is correct then the Bible is not God’s word.

We college professors are endlessly accused of indoctrinating our students. But all of the professors I know would consider it incredibly unprofessional to write a textbook like this. There are a lot of logic textbooks out there, and I’m sure their authors all had strong beliefs about something. But it would never occur to any of them to use an elementary textbook as a vehicle for pushing those views. Quite the contrary. We know that our students have a variety of political and religious viewpoints, and we usually bend over backward to avoid entangling the course material into such areas.

The far-right is so mistrustful of college professors precisely because we have a tendency to undo the indoctrination they received at home. The textbooks I saw at the convention, the present volume being just one example, illustrate that perfectly.

1. #1 MNb
January 3, 2014

We can play this game too.

According to Genesis 1:20 God first created birds and later man. According to Genesis 2:19 it was the other way round. According to the Law of Non-contradiction both cannot be true. However the Bible being God’s word is always true. God has grounded the laws of logic hence the Law of Non-contradiction is incorrect.

2. #2 Sean T
January 3, 2014

Or better yet: If god exists, then the bible is the word of god. Since the bible is the word of god, it must not contradict itself. Genesis 1:20 and Genesis 2:19 are clearly contradictory. The bible therefore is not the word of god. Since the bible is not the word of god, god therefore does not exist.

3. #3 David
January 3, 2014

Didn’t you mean “…S or C according to whether the given proposition is simplistic or…”

4. #4 Lenoxus
January 4, 2014

Rarely is so much nervous pushback concentrated into so little space. I’m pretty sure that pious folks in the Middle Ages didn’t insert God into literally every other sentence, probably because there wasn’t any paranoia about “creeping secularism” to allay.

Even if God definitely existed, this would be a lousy textbook for beginners to logic, because religion often deals with abstract stuff. Why not concrete examples like “All oranges are fruits, all fruits are plants,” etc? Or perhaps knights-and-knaves stuff, or whatever else is used in real logic textbooks (I’ve never read any). (Knights and knaves are sometimes called angels and devils; I wonder if a book like this would be more keen in talking about angels or on not talking about devils.)

Also, if God definitely existed, then a textbook like this would be silly for the continued obsession with, and insistence on, examples related to God. It would be like a conspiracy theorist writing a logic textbook in which all the examples were meant to prove that the USA government controls NASA, the State Department, etc.

5. #5 Blaine
January 4, 2014

“If evolutionary theory is correct then the biblical creation account is false. However, if the Bible is God’s word then the biblical creation account is true. Therefore if evolutionary theory is correct then the Bible is not God’s word. ”

One can only hope that it rasies these issues to the attention of the student. The quoted sentence may very well have the opposite effect on students if they are ever presented with the evidence for evolution. The fact that Michael Behe’s son is now an atheist – from reading Dawkin’s book – should give us hope.

6. #6 Walt Jones
January 5, 2014

This reminds me of an uber-Catholic I know whose arguments are primarily logical fallacies, in part because his logic professor (at a respected – by everyone – Catholic university) claimed they don’t exist; all arguments are valid. Because of this, I always feel like I’m debating Duane Gish, even when discussing seemingly innocuous topics.

Is there any validity to the professor’s position?