posted 18th May 2026
‘I want to make a difference.’
That’s a common motivation for joining a movement, campaigning for change, even for taking a job. Debate motions should make a difference, too.
Of course, they don’t actually make a difference. Yesterday lunchtime, Bryony in Year 8 dazzled her debate coach with her irresistible arguments for abolishing school uniform; this morning, she still has to pull on that itchy skirt. As the St Ethelburga’s team hold high the trophy they won at the Oxford Union by their demolition of the case for Britain’s nuclear deterrent, a fully armed submarine is still patrolling the high seas, and the prime minister is not going to order it back to port on the say so of Ayesha and Ben in Year 12. Maybe the world would be a better place if people listened more to school debaters. But as it stands, the debating club does not wield executive authority.
Nonetheless, to win a debate, you do have to show how the motion will make a difference; that it will change the world in some significant way. You need to look into the future, and predict what will happen if the motion is enacted. If you are the proposition, you need to show that this will be for the better; if you are the opposition, you need to show that this will be for the worse. This is called the impact.
The proposition need to show that the impact will be substantial and beneficial. The opposition need to show that the impact will either cause harm, or be so insignificant as to make the action of the motion not worth enacting.
Let’s see how debaters might use impact in one particular motion.
This house would tax ultraprocessed foods (UPFs)
(UPFs are sometimes known as ‘junk food.’)
Proposition argue for the following impacts, all of them beneficial. The first, short term impact leads to several further impacts, increasingly long term and increasingly beneficial.
1. Reduced consumption of UPFs.
2. Which will lead to lower incidences of obesity.
3. Which will lead to lower rates of heart disease and diabetes.
4. Which will reduce pressure on the NHS.
5. Which will also lead to people living longer, happier lives.
Opposition argue for the following impacts. The first two predict harms stemming from the action of the motion; the second two suggest that the impact of the action will be insignificant.
1. People on lower incomes, who are more likely to eat UPFs, will suffer economically.
2. The livelihoods of people working in UPF industries (e.g. serving Big Macs) will be threatened.
3. Resentment against the tax will make people less likely to adopt healthy lifestyles.
4. As UPFs are addictive, a tax will not change people’s behaviour; it will just make their habit more expensive.
Impact is an essential part of a debate, but not the whole of it. Debaters also need to consider the wider, principial issues, beyond impact - the big ideas. In the debate above, the big idea is freedom vs security; is it more important to give people security by protecting them from damaging and addictive lifestyles, or to give them freedom to make their own choices? A successful debate speech will balance the practical outcomes with a consideration of the wider ethical and moral issues.
