Most new debaters think a good argument is a good sentence. It is not. A good argument is a structure, and once you can see the structure, you can build it on command, under time pressure, on a topic you have never seen before.
The three parts of every argument
Every argument worth making has three parts. A claim states what you believe. Evidence shows why anyone else should believe it. Reasoning connects the two. Miss any one of these and the argument collapses, even if every sentence in it sounds confident.
Think of it like a bridge. The claim is the far bank you want your judge to end up on. The evidence is the material you are building with. The reasoning is the actual bridge connecting the two: without it, you have a pile of evidence on one side and a claim floating unsupported on the other.
Claim: say what you believe, precisely
A claim is not a topic. "Homework" is a topic. "Mandatory homework harms younger students more than it helps them" is a claim. The difference matters because a vague claim cannot be attacked or defended cleanly, which sounds safe but actually loses rounds: judges reward the debater who commits to something specific over the one who hedges.
Write your claim as a single sentence you could defend against a direct question. If you cannot compress it that far, you probably have two arguments tangled together and should split them.
Evidence: give someone a reason to believe you
Evidence is anything that makes your claim more credible than it would be on your word alone: a statistic, a historical case, an expert's finding, a real-world example, even a well-known consequence that your judge can verify against common sense. Not all evidence is equal. A single anecdote is weaker than a documented pattern. A source with an obvious incentive to lie is weaker than a neutral one.
New debaters often over-collect and under-select. Three strong pieces of evidence, each doing distinct work, beat ten repetitive ones. Before a round, ask what each piece of evidence proves that the others do not. If the answer is "the same thing again," cut it.
Reasoning: connect the evidence to the claim
This is the step debaters skip, and it is the one that actually wins rounds. Reasoning is the sentence that explains why the evidence you just gave supports the claim you just made. It is not a summary of the evidence. It is the logical mechanism.
Say your claim is "social media use correlates with teen anxiety, and platforms should carry warning labels." Your evidence might be a study showing anxiety rates rose alongside social media adoption. That alone proves correlation, not causation, and a sharp opponent will say exactly that. Your reasoning has to close the gap: explain the mechanism, for example that algorithmic feeds are designed to maximize engagement through social comparison, and social comparison is an established driver of anxiety in adolescents specifically. Now the evidence and the claim are actually connected by a chain a judge can follow.
A worked example
Claim: schools should teach personal finance before graduation. Evidence: a survey found most adults report never having been taught how to budget or use credit responsibly. Reasoning: financial habits form early, poor habits formed without instruction are costly and hard to reverse in adulthood, and a mandatory class is the only mechanism that reaches every student regardless of family background. Notice how the reasoning sentence does work the evidence alone cannot: it explains why teaching early, specifically in school, specifically for everyone, is the right response to the problem the evidence identifies.
Common mistakes that weaken arguments
The most frequent failure is restating the claim as if it were reasoning: "this matters because it is important." That sentence adds no logical content. A second common failure is evidence without a claim: dumping a statistic on the judge and trusting them to infer your point. Judges should not have to do your reasoning for you, and if they have to guess what you meant, they will often guess wrong, or worse, credit your opponent's interpretation instead.
A third mistake is stacking evidence that all proves the same narrow point while leaving the claim's edges undefended. If your claim covers "mandatory homework harms younger students," you need evidence that speaks to younger students specifically, not just evidence that homework can be stressful in general. Judges notice when the scope of your evidence does not match the scope of your claim, and opponents exploit exactly that gap.
Once claim, evidence, and reasoning are second nature, the next skill is spotting when your opponent's argument is missing one of them. That is the subject of the next two guides in this series.