Faulty Logic: Assumptions

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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!

Background Information

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.

Today's focus will be on using assumptions, which are beliefs that may or may not be proven.  They are related to making an inference: assumptions are based on a person's past experiences and beliefs, and inferences are derived from assumptions (plus text evidence), whether they are valid or not. Often, a fallacy occurs when an a writer or speaker makes assumptions without logical reasons.  Therefore, students have to become critical thinkers and detect fallacies in logic as they occur in speaking and writing, so that, in turn, they are able to create opinion pieces that make good use of assumptions and inferences.

Using my Assumptions Promethean Flip Chart to guide instruction, I begin by defining the concept of false logic.  False logic is an error of reasoning. When someone adopts a position, or tries to persuade someone else to adopt a position, based on a bad or invalid reasoning, they commit a fallacy.  It is important to educate students to identify logical fallacies.  Fallacious reasoning keeps students from the truth, and the inability to think critically makes them vulnerable to manipulation by those skilled in the art of persuasion.  For these reasons, Common Core educates students to think critically.

We highlight the examples on the flip chart and students share some of their ideas from their own experiences.  These conversations allow me to assess student understanding of this concept.


20 minutes

I begin this lesson by reviewing a skill my students are already familiar with:  inferencing.  We read excerpts of familiar stories and use text evidence and prior experiences to make inferences using a graphic organizer.  For example,  Goldilocks is crying.  When I cry, I am sad.  Therefore, I am inferencing that Goldilocks is sad.  After some time with guided practice completing the graphic organizer for this activity, I ask students to create fallacies in inferences that lead to  assumptions.  On the graphic organizer, I ask students not to use text evidence and just brainstorm ideas that they believe, whether proven true or not.  We begin to plot some ideas on the graphic organizer, without filling out the section on text evidence. 

After our discussions and clarification of misconceptions, I ask students to partner with someone and create a page for our False Logic Book that exemplifies Assumptions.  One partner is the illustrator, while the other partner is the author. I formatively assess students as I circulate and visit students.  It is apparent from their Assumption Student Sample that students are beginning to grasp this concept of faulty logic exemplified in assumptions.  This concept is abstract.  Therefore, plotting our ideas concretely on a graphic organizer as well as scaffolding from inferencing skills, brought this concept to a level of understanding that is  easier to grasp.


20 minutes

     We work together on brainstorming samples of assumptions.  I explain to students that assumptions are opinions that can be proven false, but stated as facts.  We discuss personal experiences of people in our lives who have expressed assumptions or opinions as facts.  We listed some examples of this type of faulty logic based on student experiences, with my guidance.  We researched together as I project websites listing samples of over-simplification from my laptop onto the Promethean board.

After reviewing the Cooperative Groups norms, roles, rules I ask students to work in teams of four to six members and cooperatively come up with one example of Assumptions to present to the class.  Each group has access to website should they wish to research examples and review the definition of assumptions.  They can cite examples from commercials, real life experiences, books they have read, etc.  I circulate to assist as needed and observe student progress.  We use the color cup system to communicate the group's need for my assistance.  This system has worked well because it allows me to differentiate instruction without impeding the collaborative process of other groups.  My availability to monitor students generate a safe and secure environment for them to take risks and try new ideas.

At the conclusion of this activity, student shared their ideas with peers via a class discussion and Assumption student presentations.  I listen and give feedback after student share their artifacts and presentations.

Students were able to grasp some of the concepts of this type of faulty logic.  However, it requires more scaffolding to reach the more abstract meaning of assumptions.   This concept requires more prior experiences and hat is what I am building with students at their young age.  Common Core requires assessing prior knowledge. However, students at this age are too young to have many life experiences.  It is my hope to create these life experiences during my lessons for future reference.