We don't choose when and where we are born, our parents or our genes. If we are very unlucky with any of those - and in many times and places, many are - we don't even live long enough to exclaim, It Isn't Fair!
Parents push the notion of Fairness as a way of settling disputes among squabbling children. It seems to work which may explain why politicians copy the strategy. I doubt it's because they have read John Rawls's A Theory of Justice .
But politicians aren't elected to be fair. They are elected to push agendas which offer benefits to some at the expense of others. So when they say (as the Conservatives were saying not so long ago)that they will reduce Inheritance Tax, that's not because it's Fair to do so but because there are lots of voters out there thinking about the big inheritance they are going to get when their Dear Parents eventually (and why does it have to be so long coming?) die. They don't want to see it taxed away. They aren't thinking about Fairness; they just want the money.
Social democratic parties have generally pushed the view that the job of government is Redistribution from richer to poorer and they have argued - or assumed - that this is the core of Fairness. This automatically creates a space for right wing parties to exclaim, Oh No It Isn't!
That is true. Justice in the nursery often involves ensuring that the small child gets the same number of strawberries as the big child - fairness in this instance is actually egalitarian, with entitlement simply based on being a person.
But justice in economic and social life is much more complicated because it has to take into account how the poor got to be poor and the rich got to be rich. Entitlement is connected to a narrative history not to abstract identity as a person. If you are poor because you spent your inheritance at the gaming table, well, Tough. It's not the government's job to tax someone (anyone, in fact) so that you can go back to the gaming table.
But suppose you didn't squander an inheritance. Suppose you just never had a chance. Isn't it the job of government to try to make life fairer than genes or parents would otherwise make it? In other words, isn't the job of government to correct life's unfairness?
One answer is that it is if by that means you can produce a better outcome for everyone. If you transfer resources from the well-off to the deprived, you indirectly benefit the better off. The streets are safer and that outcome can be achieved at a cost less than the cost of locking up the poor.
The trouble with this argument is that it simply appeals to the Prudence of the better off. It says that you can buy off trouble.
That is a belief which comes easily to an elected politician. Gordon Brown really had no other political credo than a belief that you could always buy off trouble. But someone else might reject Prudence and when warned about Trouble could simply say, Bring It On! That's what Mrs Thatcher did. That's what happens in many countries as a matter of course. But Trouble has a habit of spiralling until life becomes, for everyone, nasty, brutish and short.