Why study fallacies?
Every day you encounter arguments in advertisements, political speeches, debates, social media posts and conversations. Some are well reasoned. Others rely on logical fallacies: errors in reasoning that can make weak arguments sound convincing.
A logical fallacy is like a crack in a bridge: the argument may look solid, but it cannot hold the weight of its conclusion. Learning to recognize fallacies helps you:
– evaluate arguments critically,
– avoid being manipulated,
– build stronger arguments of your own,
– engage in fairer, more productive debates.
What makes an argument strong?
A valid argument is one where the conclusion follows logically from its premises (reasons). A sound argument is valid and has true premises.
Premise 1: All mammals are warm-blooded.
Premise 2: Whales are mammals.
Conclusion: Whales are warm-blooded. ✓
Fallacies break this logical connection.
Fallacies of relevance: attacking or distracting
Ad hominem (“against the person”)
Ad hominem attacks the person rather than the argument.
“Why should we listen to her ideas about the budget? She can’t even keep her own room clean.”
Her housekeeping has nothing to do with whether her budget ideas are sound.
Straw man
A straw man distorts an opponent’s position to make it easier to attack.
Person A: “We should reduce homework on weekends.”
Person B: “So you think students should never have to work at all?”
Red herring
Introducing an irrelevant topic to distract from the real issue.
“Why worry about pollution from the factory when there are so many problems with our schools?”
Appeal to emotion (misused pathos)
Using emotion instead of evidence, especially fear or pity.
“If you don’t buy this alarm system, your family will be in danger every night.”
Bandwagon (appeal to popularity)
Claiming something is true or good because many people believe or do it.
“Everyone is downloading this app, so it must be safe.”
Appeal to false authority
Citing someone who is not an expert in the relevant field.
“A famous hockey player says this diet cures headaches.”
Fallacies of weak induction: too little evidence
Hasty generalization
A hasty generalization draws a broad conclusion from limited evidence.
“My two friends got sick after eating sushi, so sushi is dangerous.”
Post hoc (false cause)
Post hoc (from the Latin post hoc, ergo propter hoc, “after this, therefore because of this”) assumes that because B followed A, A caused B.
“I wore my lucky socks, and we won the game. The socks helped us win.”
Correlation vs. causation
Two things happening together does not mean one causes the other.
Ice cream sales and drowning rates both rise in summer. The cause is hot weather, not ice cream.
Slippery slope
A slippery slope claims that one step will lead to extreme consequences without showing evidence for each step.
“If we let students use phones at lunch, soon they’ll use them in class, stop learning and fail out of school.”
Fallacies of structure
False dilemma (either/or)
A false dilemma presents only two options when more exist.
“Either you support this law, or you don’t care about safety.”
Circular reasoning (begging the question)
The conclusion is assumed in the premise.
“This book is the best because it’s better than all the others.”
Equivocation
Using a word in two different senses within an argument.
“A feather is light. What is light cannot be dark. Therefore, a feather cannot be dark.”
How to spot fallacies
- Identify the claim.
- Identify the reasons and evidence.
- Ask:
– Is the evidence relevant to the claim?
– Is there enough evidence?
– Does the conclusion follow logically?
– Are opposing views represented fairly?
– Are there hidden assumptions? - Name the fallacy if one exists, and explain why the reasoning fails.
Responding to fallacies
When you encounter a fallacy in a discussion:
– Stay calm and focused on the reasoning, not the person.
– Point out the gap: “That’s an interesting example, but two cases aren’t enough to show a pattern.”
– Redirect to the actual issue: “Let’s focus on whether the policy works.”
– Ask for evidence: “What data shows that one step leads to the next?”
Avoiding fallacies in your own writing
- Support claims with sufficient, relevant evidence.
- Represent opposing views accurately and fairly.
- Distinguish correlation from causation.
- Consider multiple options, not just two.
- Critique ideas, never people.
Worked example
Argument: “Our town should not build a new skate park. The last time teenagers had a place to hang out, there was graffiti downtown. Besides, the people supporting this are just kids who want to skip homework. If we build it, crime will increase, property values will fall and families will move away.”
- Graffiti downtown → hasty generalization / post hoc: one incident does not prove the park causes graffiti.
- Kids who want to skip homework → ad hominem and straw man.
- Crime increase → property values fall → families move → slippery slope: no evidence for each step.
A stronger counterargument would use data from other towns with skate parks and address cost, location and supervision.
Try it yourself
Name the fallacy.
- “You can’t trust his opinion on climate change; he failed science in high school.”
- “Either we cancel the field trip, or students will get hurt.”
- “Since the new principal arrived, test scores dropped. She must be a bad principal.”
- “Millions of people use this supplement, so it must work.”
- “Video games are violent because they contain a lot of violence.”
Answers: 1. Ad hominem. 2. False dilemma. 3. Post hoc (false cause). 4. Bandwagon. 5. Circular reasoning.
Study tip
Make a set of fallacy cards with a name, definition and example on each. Watch a debate or read comments on a news article and see how many fallacies you can identify.
Quick recap
- Logical fallacies are errors in reasoning that weaken arguments.
- Relevance fallacies distract or attack: ad hominem, straw man, red herring, bandwagon.
- Weak-evidence fallacies overreach: hasty generalization, post hoc, slippery slope.
- Structural fallacies distort logic: false dilemma, circular reasoning.
- Spot fallacies by checking relevance, sufficiency and logic, and avoid them in your own writing.