Labour's election slogan, “a future fair for all”, was vacuous. No surprise there, I suppose: it was an election slogan after all. Fairness is one of those ideas that fails a basic test in a slogan or a mission statement – could you imagine anyone campaigning for unfairness? Moreover, fairness means very different things to different people.

For instance, if Sue earns ￡20,000 and Jane earns five times as much, ￡100,000, what's the fair burden of tax? An extreme libertarian view is that all tax is armed robbery from the biggest gangster of all, the government. An extreme utilitarian view is that as long as Jane's post-tax income is greater than Sue's she has less need of the money and should be the first port of call for any extra taxation. It would be perfectly fair, under this view, for Jane to pay 75 per cent tax and Sue to pay nothing, and the only objection would be the practicalities.

I have a grudging respect for both sides of this argument. But in reality, we fudge a middle ground. Most people seem to think that it's reasonable for Jane to pay a higher percentage of her income as tax than Sue does. But some would say that if Jane pays ￡10,000 and Sue pays ￡3,000, Jane has contributed more than her fair share, even if the average tax rate she faces is lower. Further confusing the issue are taxes on fuel, cigarettes, air fares and other items which are correlated – imperfectly – with a particular level of income.