The politics of the benefits cap
It's fair. It's popular. It's moral to ensure that families in which people are unemployed but able to work should not get more in benefits than the average family can earn.
It's arbitrary. It takes no account of the differences in rents and standards of living in different parts of the country. It's immoral to force vulnerable families out of their homes.
That, in summary, is the debate about the benefits cap taking place in the Lords.
Cuts that are already affecting hundreds of thousands of people and saving billions of pounds have been agreed with scarcely any debate and yet today a proposal which saves relatively little - £290m a year out of a total work and pensions budget of £192bn - and affects around 1% of claimants - approx 67,000 families - has become the focus of the welfare debate.
Labour have just signalled that they are ready to vote with the bishops and some Lib Dems who are trying to limit the impact of the benefits cap by excluding child benefit and, therefore, removing the penalty/disincentive (depending on your point of view) to have large families whilst on benefit.
The Tories are delighted - win or lose today they will claim that Ed Miliband is soft on welfare and opposes cuts just days after saying he recognised the economic realities.
Labour will reply that his party are not against a cap but are simply not prepared to vote for one which increases homelessness.
Ministers hint that they will bring in transition arrangements to avoid penalising the poorest but refuse to spell out what they are.
It is all too clear that this debate is as much about politics as it is about benefits.