Social mobility - it is right up there at the top of the coalition agreement.
David Cameron and Nick Clegg say in their foreword to the document that they want to see social mobility "unlocked".
Schools, and a much-needed strategy for "gifted and talented" pupils, will be the keys to the door in England.
But it will be developments in university admissions that show whether the door is merely ajar or wide open.
And it is here that arguments rage over "social engineering".
We had a taste of that this week in the reaction to the report from Offa, the Office for Fair Access, which looked at entry to the most selective universities.
Offa found that the wealthiest 20% of students were seven times more likely to go to the top universities than the poorest 40%.
It also found that this gap had not closed since the mid-1990s.
It carefully avoided calling for positive discrimination in admissions.
Instead, it said, more should be done to identify and guide bright pupils, as young as 14, who might not otherwise aim for elite universities.
But for the Daily Mail this raised the spectre of "social engineering".
It quoted one independent school head teacher who said it would be an "extraordinary world where we penalised pupils for being too successful".
So where are we on university access? And what effect will the coalition government's policies have?
The first thing to clarify is that the Offa report related only to the UK's most prestigious universities.
Across the higher education sector overall, the picture is very different.
There has been real progress in getting more young people from disadvantaged homes into university generally.
The likelihood of young people from the most disadvantaged areas becoming undergraduates has increased 30% over the past five years.
The gap between the most disadvantaged and the most privileged students has finally started to narrow.
And this has not been at the expense of the middle-class students, whose chances of going to university have risen 5% over five years.
Since most were already going to university, any further increase is quite an achievement.
So the wider picture suggests real progress on social mobility. But the narrower picture in the most selective universities suggests something different.
Future policy will need both to maintain progress in the former and start to tackle the latter.
But there are obstacles ahead - the biggest is the threat of an end to university expansion.
The last government's target of getting 50% of young people into higher education received a hostile press, partly because of its arbitrary nature.
Labour never reached its target, although it made progress towards it and ministers claimed it was more aspiration than destination.
Now some 45% of young people enter university. This growth was a major factor in improving access to poorer students.
It has, indeed, been a rising tide that floated all boats even though, as we have seen, it did not help many of the more modest dinghies into the swankier marinas.
Now though, we face the prospect of the tide receding if the government abandons further expansion.
Abolishing the 50% target has been the policy of both coalition parties in the past and was explicit in the Lib Dem manifesto.
Interestingly, though, the pledge was not repeated in the coalition agreement.
Their opposition to the target was mostly about its artificiality, rather than a wish to reduce the numbers entering university.
Indeed the Conservatives had planned an extra 10,000 university places this summer (although they were trumped by Labour's last Budget which created an extra 20,000).
But we are now entering a period when the lack of cash will shape policy.
With public spending cuts imminent there must be serious doubts whether university expansion can continue over the next few years.
And that would hit wider access.
However, the coalition government's silence on the 50% target may be a sign they now realise that Labour's aim was not over-ambitious but too modest.
While UK universities have expanded, other countries have grown at an even faster rate.
In 2000 the UK had the fourth highest graduation rates in the OECD countries. By 2006 it had fallen to eleventh place.
Several countries now send more than 60% of their young people to university. These include Australia, Hungary, Iceland, New Zealand, Norway, Poland, Sweden, the US and Russia.
Meanwhile, India and China are building hundreds of new universities to accelerate their graduation rates.
Does the UK really want to fall further behind?
Squaring the circle
If we do not, we have to decide how to fund expansion if the Treasury will not, or cannot, pay.
That is why the future of student finance is such a thorny issue for the coalition.
During the election, the Conservatives conveniently hid behind the independent Browne Review, which was charged by the last government with examining future university funding.
It reports in the next few months. The coalition agreement says the government will judge its proposals against the need to increase social mobility and the need to consider the impact on student debt.
This is a tough call. Few politicians have a harder task than the new universities minister, David Willetts.
Adding to his challenge, is his agreement that Offa's report has highlighted "a weak point" in the system that must be improved.
So, the new government needs a new approach to universities that both continues the recent progress in widening participation across the whole sector and tackles the problem of access to the most selective universities.
This is at a time when it looks inevitable that students (or more accurately graduates) will have to foot a bigger portion of the bill for their university education.
Can ministers square the circle?
There are some interesting ideas floating around that might mitigate the effect of raising fees on poorer students.
The Sutton Trust, for example, has suggested that students from the poorest homes should get a fee-free first year at university to encourage them to dip their toes in the water.
The Browne Review, or the government's response to it, must find ways to raise more money to fund expansion but without doing so in a way that deters poorer students.
Only that way can the advances in university access generally be maintained and a start be made on closing the gap between rich and poor entering the most prestigious universities.
Cameron and Clegg's promise to unlock social mobility is a tall order in these straitened times.
Mike Baker is a freelance journalist and broadcaster.