What a fallacy is
A fallacy is a mistake in reasoning that can make a weak argument sound strong. Learning to spot them is one of the most useful things a debater can do, and the Logic Ladder teaches each one with practice. This chapter is about using them in a round.
The ones you'll hear most
| Fallacy | In a round it sounds like | How to answer |
|---|---|---|
| Straw Man | “The affirmative wants to ban all homework.” (They proposed a limit.) | “That’s not our case. We said ___, and they haven’t answered that.” |
| Attacking the Person | “Of course they’d say that; their evidence comes from a group that supports the policy.” | “Where evidence comes from matters, but they haven’t shown our numbers are wrong. The data are from ___.” |
| False Dilemma | “Either we fund space exploration or we feed the hungry.” | “Those aren’t the only choices. A budget can do both; the question is how much of each.” |
| Slippery Slope | “If we lower the voting age to 16, next it’ll be 12.” | “They haven’t shown any step in that chain. Each one would need its own vote and its own reasons.” |
| False Cause | “After the city raised the minimum wage, restaurants closed, so the wage caused the closings.” | “Timing isn’t cause. What else changed that year? Studies that compare similar places find ___.” |
| Hasty Generalization | “My school tried a four-day week and grades dropped.” | “One school is a tiny sample. Studies of many districts find ___.” |
| Appeal to the People | “Most Americans support it, so it works.” | “Popular and effective are different questions. Here’s the evidence on whether it works.” |
| Appeals to Authority: Fair and Unfair | “A famous athlete says this diet is best.” | “Is that person an expert on this question? Here’s what qualified experts say.” |
| Red Herring | Asked about cost, they talk about how important the goal is. | “The goal isn’t in dispute. The question was cost, and they still haven’t answered it.” |
| Weak Analogy | “A country’s budget is just like a family’s.” | “Name the difference that matters: governments can ___ and families can’t.” |
| Equivocation | Using “free” to mean “no tuition” and then “costs nobody anything.” | “They’ve used one word two ways. Free to the student isn’t free to taxpayers.” |
| Complex Question | In cross-ex: “Why does your plan ignore rural schools?” | “It doesn’t. Here’s how it covers them.” |
| Appeal to Ignorance | “No one has proven it’s unsafe, so it’s safe.” | “Lack of proof isn’t proof. They have the burden here, and they haven’t met it.” |
| Suppressed Evidence | Reading a study’s benefits and skipping its costs. | “The same study also found ___. Here’s the full paragraph.” |
| You Too (Tu Quoque) | “They say our plan is expensive, but theirs costs money too!” | “Both cost something; the question is which is worth it. Compare the two.” |
Calling out a fallacy
Naming a fallacy isn’t enough. “That’s a slippery slope!” tells the judge you know a term, not why the argument fails. Say what’s missing: “They need evidence that each step follows, and they have none for the second step.” Many judges, especially lay judges, respond better to the plain explanation than to the Latin name.
Be careful, too, about calling everything a fallacy. Some arguments that look like fallacies are good reasoning: a chain of consequences with evidence for each link isn’t a slippery slope, and quoting a qualified expert isn’t an unfair appeal to authority. The Logic Ladder’s Good Reasoning That Looks Like a Fallacy and Telling Look-Alike Fallacies Apart help you tell the difference.
Keeping them out of your own case
- Before a tournament, read your case as if you were the other side, looking only for fallacies.
- For each causal claim, ask: what else could explain it?
- For each example, ask: is it typical?
- For each “if this, then that” chain, ask: do I have evidence for every link?
- For each restatement of the other side, ask: would they agree that’s their view?
Practice
- Try the fallacy spotter in the drills.
- Write one fallacious argument and one fair argument on the same topic, and see whether a partner can tell which is which.
- Listen to a political speech or an advertisement and find one fallacy; explain in a sentence why the reasoning fails.
Sources
Updated 2026-10-25.