A logical fallacy is not just a "bad argument" in a vague sense. It is a specific, recognizable pattern where the reasoning fails even if the conclusion happens to be true. Learning to name these patterns does two things for you: it lets you take them apart quickly in a live round, and it stops you from accidentally using them yourself when you are under time pressure and reaching for anything that sounds persuasive.
Straw man: attacking a weaker version of the claim
A straw man replaces your opponent's actual position with an easier one to knock down. If your opponent argues "we should regulate social media algorithms for minors," and you respond "so you want to ban the internet for teenagers," you have not engaged with their claim. You have built a weaker one and beaten that instead.
The fix, whether you are catching this in an opponent or avoiding it yourself, is to restate the other side's claim in a way they would agree is fair before you respond to it. If you cannot state their position accurately, you are not ready to attack it.
Ad hominem: attacking the person instead of the claim
An ad hominem dismisses an argument by attacking the person making it rather than the argument itself. "You would say that, you're on the debate team" is not a response to a claim, it is a distraction from one. This fallacy is tempting because it often gets an emotional reaction from a live audience, but a trained judge will notice that the underlying claim was never actually addressed and will penalize the debater who dodged it.
There is a related, legitimate move that looks similar but is not a fallacy: pointing out that a source has a documented conflict of interest is a real critique of evidence quality. The difference is whether you are attacking the argument's support or just the person's character.
False dilemma: hiding the other options
A false dilemma presents only two options when more exist, usually to make one option look inevitable. "Either we cut the program entirely or the budget collapses" ignores every version of partial funding, restructuring, or phased cuts in between. Debaters reach for this because two options are easier to argue than five, but a sharp opponent only needs to name one overlooked option to break the whole frame.
Slippery slope: assuming the worst outcome is inevitable
A slippery slope argument claims that one step will inevitably lead to an extreme outcome, without establishing the actual mechanism that would cause each step to follow the last. "If we allow students to redo one failed test, eventually no test will mean anything" skips over every safeguard that could stop that chain: grading policy, teacher discretion, a limit on retakes. The fallacy is not that slopes never exist. Some causal chains really are that tight. The fallacy is asserting the chain without showing why each link actually holds.
To catch this fallacy in a round, ask your opponent to walk through the mechanism step by step. If they cannot explain why step two follows from step one, the slope was assumed, not argued.
Correlation treated as causation
This is the most common fallacy in evidence-heavy debates, and it deserves its own mention. Two things happening together does not mean one caused the other. Ice cream sales and drowning deaths both rise in summer, but ice cream does not cause drowning: heat drives both. Whenever an opponent presents a statistic showing two trends moving together, ask what else could explain the pattern before accepting their causal story.
Appeal to popularity: treating agreement as proof
An appeal to popularity argues that a claim must be true because many people believe it, or that a policy must be right because it is popular. Popularity can be relevant evidence about what people want, which sometimes matters, but it is not evidence that a claim is factually correct. Widespread belief has been wrong before, often enough that "everyone agrees" should never be the last line of your reasoning.
Using this in a live round
You do not need to shout "straw man!" like a buzzword to win the point. Instead, name the pattern briefly, then explain the actual gap: "that response addresses a stronger claim than the one I made, here is what I actually argued." That sentence does more work than the label alone, because it shows the judge exactly where the reasoning broke down rather than assuming they will take your word for it.
The next guide in this series covers how to turn a spotted fallacy, or any weak point in an opponent's case, into a rebuttal that actually moves the round in your favor.