Faulty Logic: Self-Contradictions

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SWBAT write examples of opinions with errors in reasoning about a given topic.

Big Idea

Students use critical thinking skills to detect faulty logic in arguments. Non-examples help students learn, too!

What is Self-Contradiction

20 minutes

In order to teach the Common Core writing standards of using reasoning to support opinions, I guide students to explore faulty logic examples in this unit.  Faulty logic is an argument that lacks validity. It is sometimes referred to as paradoxical reasoning because it is illogical, absurd, or contradictory.  Not only will they need to recognize faulty logic so as to avoid using it in their own opinion writing, later they will also be expected to assess reasoning provided by the author and determine if the evidence is based on fallacious reasoning as they enter middle school and high school in preparation for research in their careers or college. Students need to build on prior knowledge to get to that point.  Starting to introduce errors in logic in the primary grades gives students the foundational knowledge needed for this critical reasoning later on.

Although the concept of faulty logic and errors in reasoning is not often taught until later grades, I decided to present my gifted, high achieving class with this challenge.  It is an experiment of sorts for my class consisting of students who are out-of-the-box thinkers. The tricky part is teaching students through non-examples. This non-traditional route of teaching shows students what not to do instead of what to do.  Students use critical thinking skills as they analyze the irrationality of their writing. This activity is a demonstration of the old adage "Learn from your mistakes." Indeed, mistakes provide opportunities for learning.

This lesson is the one of the firsts in our unit of Faulty Logic.  I began this lesson by showing my Faulty Logic: Self-Contradiction Flip Chart, which teaches about one of four type of Errors in Reasoning.  Then, I introduced the seven types of Faulty Logic we will be discussing in this unit, but focused primarily on the definition and examples of today's focus type of Faulty Logic called "Self-Contradictions."  Students are shown images and examples of Self-Contradiction to examine the characteristics they all had in common.

The day before, I asked students to pay attention to television commercials while they are watching their favorite shows.  I asked students to pay careful attention to what the commercials are trying to get them to buy or to do.  Then, I asked students to pay attention to the supportive evidence given during these commercials.  Did they make sense?   We discussed and viewed a Self contradiction commerciall example that I downloaded so that the students and I can examine the together for faulty logic.

This lesson focuses on the writing standard of writing opinion pieces supplying reasons that support the opinion.  Only in this case, the supports are non-examples because they are faulty logic or illogical.

Creating an Self-Contradictory Advertisement

20 minutes

Students brainstorm ideas as I model creating an "advertisement" that displays self-contradiction.  We started our discussion with oppositional views such as:  "The only thing that is certain is uncertainty,"  We underline the opposite words certain and uncertain.  I show a list of examples from the flip chart and we wrote the words that are opposites or antonyms so students can see the structure and pattern of self-contradictory statements.

I ask students to create their own "commercial" on paper that is called an "advertisement."  We talked about products or services that students are trying to sell in their advertisement.  Then, we brainstormed ways to exemplify self-contradiction.  Students are able to make connections if they relate self-contradiction to their prior experiences with the concept of antonyms or opposites. 

Then, I send students to create their advertisements using a blank sheet of letter size paper and crayons/markers.  Students work on their self-contradicting advertisements as I facilitate as needed.  Students find this activity engaging.  They often have a good laugh because they think they are asked to do something silly or nonsensical.  How often does the teacher ask students to create an artifact that is illogical?  Students often have a great deal of fun with this very unusual activity.

Sharing our Advertisements

20 minutes

Once students have completed their creations of Self-Contradictory Advertisements, we gather together to share out.  As evident in their work samples (Advertisement sample 1, Advertisement sample 2,  Advertisement Sample 3), students were creative in their advertisements showing self-contradiction.  The Contradiction Student Presentation indicates a student's ability to communicate that knowledge as well.  Our discussion focuses on what we have learned about the accuracy of supportive evidence after this activity.  Students are now aware of one way to critique evidence and not always look at information at face value.


10 minutes

    After students had practice with this concept, I extended this lesson to give complete ownership to students. I ask students to recall and explain information learned by conducting an activity on Contradiction Reciprocal Teaching.  A student volunteers to teach the class about self-contradiction.  Reciprocal teaching gives students opportunities to communicate conceptual knowledge with their peers.  It also gives me opportunity to conduct formative assessments as I actively listen for accuracy of information.