Why weighing decides rounds
By the last speeches, each side usually has an argument or two still standing. If you only say “we win our argument,” the judge has to decide on their own which argument matters more, and they may not choose yours. Weighing is comparing impacts out loud so the judge doesn’t have to guess.
Weigh comparatively: not “our impact is big,” but “our impact is bigger than theirs, because…”.
Four common ways to weigh
| Measure | The question | Sounds like |
|---|---|---|
| Magnitude | How big is it? How many people, how much harm or good? | “Their impact affects one district’s budget; ours affects every student’s health.” |
| Probability | How likely is it to happen? | “Their harm needs four things to go wrong in a row; ours is already happening.” |
| Timeframe | How soon does it happen? | “Students lose sleep starting the first week; their cost shows up years from now, if ever.” |
| Reversibility | Can it be undone? | “A bad budget year can be fixed next year. A lost species can’t be brought back.” |
When measures point different ways
Often one side has a huge but unlikely impact, and the other a smaller but near-certain one. Neither measure wins automatically. Make the case for your measure: “A one-in-a-million risk shouldn’t outweigh a certain harm to thousands of students today,” or “Even a small chance of an irreversible disaster deserves more weight than a modest, fixable cost.” Good judges listen for which side explains its measure better.
An example
Pro Two impacts are left: their risk of an accident and our reduction in air pollution from fossil fuels. Weigh probability: air pollution from burning fossil fuels harms health every day, while serious nuclear accidents are rare. Weigh magnitude: pollution affects millions of people, not one region. So even if they’re right that accidents are possible, our impact is certain and larger.
Con Weigh reversibility and timeframe. New reactors take many years to build, so their benefit is slow to arrive, while wind, solar and efficiency can cut emissions sooner. And a major accident can make an area unusable for a long time, which can’t be quickly undone. When one option is slower and carries an irreversible risk, the judge should prefer the faster, safer path.
Both sides weighed using different measures and explained why their measure should count most. That gives the judge a clear choice.
Weighing words that help
- “Even if they win ___, we still win because ___.”
- “Prefer our impact on probability, because ___.”
- “Their impact depends on ours: if ___, then their harm never happens.” (This is called short-circuiting or pre-requisite weighing.)
- “This is the bigger issue because it affects more people for longer.”
Practice
- Take two impacts from opposite sides of a topic page and write one weighing sentence for each of the four measures.
- Write a 30-second “even if” statement that weighs your impact against the other side’s strongest one.
- Use the weighing practice in the drills.
Sources
- Impact calculus, Wikipedia. Accessed 2026-10-25.
- Impact Calculus, Philomathean Society, Phillips Academy Andover. Accessed 2026-10-25.
Updated 2026-10-25.