We’re having a general election here in the UK, and so there has been more than the usual amount of talk about “fairness”. Fairness is one of these slippery words, the definition of which depends very much on your worldview. But ignoring even that, I’d like to propose a new rule to be observed in political debate, worldwide:

Politicians should be banned from arguing for change using the words “fair” or “fairness” unless they also specify what level of change would be “unfair”.

Let’s take the common example of taxes. We often hear phrases like “the rich should pay their fair share”, or “it’s only fair that those with the most resources shoulder the burden”. If a politician says this, they need to be asked “OK – so what level of taxation would go beyond ‘fair’ and get into ‘unfair’?” They would be allowed to define it in any number of concrete ways, e.g. “I think it’s unfair to take more than 50% of a person’s total income”, or “I think it’s unfair to leave anyone with less than £15k of income after tax”.

But the one answer that should not be allowed is the equivalent of “‘fair’ means paying more than they pay at the moment”, however much that is. In those cases, talk of fairness is actually covetousness in disguise – people are being taxed simply because they have money and the politician wants some of it for their own purposes. Covetousness knows no limits. If they want to argue for this, they can – but they should not have the gall to try and call it ‘fair’.

Politicians don’t like making such commitments, because then they would have to (shock!) keep them, or be easily held accountable. But the convenient thing about “fairness” is that it’s very elastic – people can generally be convinced to agree that any tax rise is ‘fair’, as long as it doesn’t target them. After all, most people like the idea of spending other people’s money on stuff that they want to happen. But without any sort of upper limit defined, taxpayers can never know when a particular politician might be coming back for another bite of their earnings – and that most certainly is unfair.