Abigail knocked on my office door.
'Mr Bell,' she said, 'I've got a problem.'
'What's that, Abigail?'
'I'm due to speak in a debate at lunchtime today. But my music teacher says I have to come to an important rehearsal for our orchestra before the concert tonight.'
'That's all right, Abigail. Give your debate partner your notes, and she can speak twice in the debate.'
'But I don't want to let her down.'
'You don't want to let the orchestra down either. How many people are there in the orchestra?'
'About forty.'
'Isn't it better to let down one person than to let down forty people?'
'Ah,' said Abigail. 'Utilitarianism.'

Abigail had been listening in Philosophy class. Utilitarianism covers a whole range of different philosophical approaches, but they all agree on two things. First, what matters is not whether an action is fair or moral in itself, but what consequences follow from the action; secondly, we should always aim for the greatest good of the greatest number. It is a very practical, almost mathematical, way of approaching problems.

Let's look at how you might apply utilitarian thinking to a debate motion. Say the motion is This house would abolish private schools. For the proposition, one approach would be to argue that private education is fundamentally unfair; that it is morally wrong that some children should have advantages over others because of who their parents happen to be. A utilitarian approach would not be bothered about fairness. Instead, it would argue that abolishing private education would produce better outcomes for society as a whole. Currently, the best teachers and the best facilities are concentrated in a very small minority of schools, benefitting only a very small minority of children; if we spread these resources more widely, more children would be better educated, and the economy would be more successful on account of having a better educated workforce, to everyone's benefit.

Similarly, the opposition could also argue on grounds of fairness; they could say it is fundamentally unfair to prevent parents from educating their children as they see fit. But if the opposition want to take a utilitarian approach, they could argue that more people will be benefited if the people in top jobs get the benefit of private education, because those people have more influence over society as a whole. It's actually a good thing that most judges, journalists, politicians and CEOs went to private school, because it means that they are better prepared for these important jobs, in which they make much more difference to everyone's well being than people in lower paid jobs do.

Utilitarianism has its limitations. At its most extreme, it can lead to some pretty shocking ideas. You could, for example, argue on utilitarian grounds that anyone diagnosed with a terminal illness should immediately be killed by their doctor; why waste the resources of the NHS on someone who has nothing left to give to society? The calculations involved are rarely as simple as Abigail's balancing of one debater against forty musicians; how exactly do you quantify the impact of an extra science lab or rugby pitch on the economy in twenty years' time? However, it is very useful for debaters to be aware of utilitarianism, whether as a tool for forming their own arguments, a way of analysing the other side's arguments, or just as a way of thin