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Logic Q & A #2

by Hans Bluedorn


1. Quiz answer

2. Fallacy Detective Test

3. Logic activities for younger students

4. Predicate calculus

5. Formal logic

6. Creating a formal logic book

Quiz Answers

The correct answer to last time’s quiz was the fallacy “post-hoc-ergo-propter-hoc” or sometimes called “false cause.” Post-hoc-ergo-propter-hoc is when someone concludes that since A happened before B, then A must have caused B. this fallacy also occurs when somebody says that since A and B are commonly seen together, one must have caused the other.

The researchers in the article notice that murder rates, abortion, promiscuity and suicide are higher in the United States, which is a more religious nation than most European nations that have both a lower crime rate and a lower church going population. The researchers then conclude that since more religion is seen with higher crime rates etc., the religion must have caused the crime. Post-hoc-ergo-propter-hoc.

The quiz was won by Carter Askren, who will receive a Fallacy Detective T-shirt.

Hans Bluedorn


Do homeschool parents qualified as "teachers" for your Fallacy Detective test?

I read a post from a lady in a homeschool board, where she mentioned that "to her" using the Thinking Tool Box BEFORE the Fallacy Detective was there an specific, necessary order to obtain the best results from your products?



Yes, we will send The Fallacy Detective Test to homeschool parents. However, since the test is copyrighted, you must send us a request for it in order to receive it. You are not allowed to reproduce it except for you own homeschool/class.

We recommend parents use The Fallacy Detective before The Thinking Toolbox. However, this is not necessary. We believe TFD is easier than TTT.

Hans Bluedorn


Re:  logic activities for younger students

I’ve used products from the Tinman Press for several years now with early and late elementary age children.  While most of their products would work well in the classroom, they can also be used individually.   The kids love the activities, and they really are great logic-building activities.

I’ve also used lots of materials from the Critical Thinking Company.  Their web site is searchable by grade level.   I saw that some families recommended using the Mind Benders, and they are good.  But there are lots more materials available for younger folks.

Anni Welborne

West Lafayette, IN


Hans and Nathanial,

I was wondering if you could tell me what predicate calculus is?  What type of logic is it?  I know of someone who is using her training in this subject (she took a class) to make herself into an expert on everything in life. Help please!

Anne Calvert


Predicate calculus is an advanced form of modern symbolic logic.

If your friend says that she knows more than you do because she knows logic, then she is fooling herself. Logic should teach humility. People with good thinking skills know they are not smarter than other people.

If she knows this advanced form of logic, she should be able to translate all her new ideas into something you can understand. If she can't translate things into something that convinces you, then her advanced form of logic is useless. What is the difference between someone with such incredibly DEEP thoughts that we can't understand them, and someone with incredibly CONFUSED thoughts that we can't understand?



Dear Logic Guys,

Logic is a required class in the classical christian school my daughter attends. Logic instruction begins in seventh grade. This current class is working through Douglas Wilson's workbook Intro to Logic. At this point a few students are riding through, my daughter is not. I find this text and the language and concepts to be difficult. How do young students wrap their brains around these concepts? Any suggestions? Which of your materials would best complement the Wilson text?

Thank you,

Cynthia Brandon


We suggest using Wilson and Nance's "Introduction to Logic" (which teaches formal logic) at age sixteen or seventeen. Some younger students handle it if they have a knowledgeable teacher to answer their questions and guide them.

There is no hurry about logic. It is more important that students learn to enjoy logic and thinking skills and that they understand what they are learning. You can think of formal logic as being about as difficult as geometry. If the first thing a student learns in math is geometry, he may feel overwhelmed. It may be easier to start with something less challenging that beginners can have fun with.



Are you planning to write a formal logic book? We are starting to use Introductory Logic by Wilson and Nance.We are enjoying it, but my son loves your books even more!!

Thank you.


Mexico City.


We aren’t planning a formal logic book right now. However, we are thinking about creating a Fallacy Detective video. What do you think about that idea?

Copyright October 13, 2005, all rights reserved. 5380 views

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