Philosophy: Logical Fallacies: Common Errors in Reasoning
Identifying weak arguments and improving reasoning
Philosophy: Logical Fallacies: Common Errors in Reasoning
Identifying weak arguments and improving reasoning
Philosophy - Grade 6-8
- 1
A student says, "You should not listen to Maya's idea about recycling because she forgot to bring her lunch yesterday." What logical fallacy is this, and why is it weak reasoning?
Look for whether the argument criticizes the idea or the person.
This is an ad hominem fallacy because the student attacks Maya instead of responding to her idea about recycling. It is weak reasoning because forgetting lunch does not show that her recycling idea is wrong. - 2
Coach Lee says, "If we cancel one practice for rain, soon nobody will ever come to practice again." What fallacy does this argument most likely use? Explain your answer.
This argument most likely uses the slippery slope fallacy. It assumes that one canceled practice will lead to an extreme result without giving evidence that this will happen. - 3
Read the argument: "Everyone in my class has the same backpack, so it must be the best backpack in the world." Identify the fallacy and explain what evidence would make the argument stronger.
Popular does not always mean correct or best.
This is a bandwagon fallacy because it says something is best just because many people use it. The argument would be stronger with evidence about the backpack's quality, comfort, price, and durability. - 4
Jalen says, "We should either spend all our class money on a party or spend none of it and have no fun at all." What fallacy is shown here, and how could the choices be stated more fairly?
This is a false dilemma because it presents only two choices when more choices may exist. A fairer statement would include options such as spending part of the money on a small party and saving the rest. - 5
A cereal ad says, "Famous actor Riley Star eats Crunchy Oats, so Crunchy Oats must be the healthiest cereal." What fallacy is this? Explain why the actor's opinion is not enough.
Ask whether the person is a real expert on the topic.
This is an appeal to false authority because a famous actor is not necessarily an expert on nutrition. The actor's opinion is not enough because health claims need evidence from ingredients, nutrition facts, or reliable experts. - 6
Read the argument: "I wore my lucky socks during the math test, and I got a good grade. The socks caused my good grade." What is the reasoning error?
This is a false cause fallacy because the argument assumes the socks caused the good grade just because both things happened together. The good grade may have been caused by studying, paying attention, or understanding the material. - 7
A classmate says, "People who want shorter homework assignments just do not care about learning." What fallacy is this? Explain how the classmate misrepresents the other side.
A straw man argument makes someone's view easier to attack by describing it unfairly.
This is a straw man fallacy because the classmate changes the other side's position into a weaker version. Wanting shorter homework does not necessarily mean students do not care about learning. - 8
Study this claim: "This phone case must be strong because it is the toughest case, and I know it is the toughest because it is strong." What fallacy is being used?
This is circular reasoning because the claim uses the same idea as both the reason and the conclusion. It does not give independent evidence that the phone case is strong. - 9
A student says, "My cousin tried one science video online and it was boring, so all science videos are boring." Identify the fallacy and explain what is wrong with the conclusion.
Look at whether there are enough examples to support the conclusion.
This is a hasty generalization because the student makes a broad claim based on only one example. One boring video does not prove that all science videos are boring. - 10
Read the argument: "You cannot trust the new library rules because they were suggested by students, and students always want easy rules." What are two problems with this reasoning?
One problem is that the argument attacks the group of students instead of judging the rules themselves. Another problem is that it makes an unfair generalization by saying students always want easy rules. - 11
Match each fallacy to the best example. Write the letter of the example beside each fallacy. 1. Bandwagon 2. False cause 3. Ad hominem A. "The team won after I changed seats, so my seat change caused the win." B. "That idea is bad because the person who said it has messy handwriting." C. "Everybody is buying this game, so it must be the best game."
Focus on the kind of mistake each example makes.
The correct matches are 1-C, 2-A, and 3-B. Bandwagon uses popularity as proof, false cause assumes one event caused another without enough evidence, and ad hominem attacks the person instead of the idea. - 12
Rewrite this weak argument so it uses better reasoning: "Our school should get new water fountains because anyone who disagrees hates clean water."
A stronger argument would be: "Our school should consider getting new water fountains because some current fountains are old, slow, or hard to use, and students need easy access to clean drinking water." This version gives reasons without attacking people who disagree.