My father, Ralph, used to describe himself as a socialist who happened to be an academic, not an academic who happened to be a socialist. It meant that, for him, academia was not about arid analysis of obscure problems, but an attempt to change the world we live in.
The Spirit Level by Richard Wilkinson and Kate Pickett is a book in the best of that tradition. The argument that more equal societies do better on everything from infant mortality to depression naturally provoked a backlash from the right. Some claimed that the results are unreliable - skewed by the extremes of Scandinavia and America, say. Some that even if the results are true, there is nothing to be done: inequality is a characteristic of all countries and the changes required are not worth the effort.
All the claims to undermine their work have brought forth strong counter-arguments from the authors. Armed with multiple studies across each area of analysis, they show, for instance, that inequality is linked to ill-health across the United States, the counties of Chile, the regions of Russia and the provinces of China - not just comparing America and Scandinavia.
And countering the second claim - that there is nothing to be done - is something Pickett and Wilkinson have tried to do. But in fact, it is not just for them, but for us: we, politicians and the public, have to decide what kind of society we want to live in, and whether the difficult task of greater equality is worth the candle. It is - and it is at the very heart of why we need to move on from New Labour. During our years in power, we didn't do enough to stop the gap between rich and poor getting wider. If you really believe in a society where there is social mobility, where we look after each other, where we build social solidarity, then the gap matters.
Yet we all know that the challenge we face is not to convince ourselves, but to convince others. Some will say that though their heart is in favour, their head says a more equal society will always run into the electoral sands. This is old thinking that ignores the way the world has changed and where the public is - but we do need to understand how to win the argument for equality.
First, we have to build an appeal to equality in people's lived experience, not in management consultancy or technocratic-speak about Gini coefficients. The daily struggle of people working all the hours that God sends, not having time to see their kids, feeling stressed out about their life, is the reality of low pay.
My campaign for the living wage speaks to that daily experience - and the intuition, shared by most people, that fairness means a decent day's pay for a decent day's work - and the fact that responsibility is not just about individuals, but about companies paying a fair wage.
Second, we have to understand where the common ground of politics is, and how we build on it. New Labour began as the party of the windfall tax - and ended up defending bankers' bonuses. The public was ahead of us, as so many of us saw on the doorsteps at the general election. We became locked in to efforts to "decontaminate" the party brand from the problems of the 1980s, even as the public had moved on to concerns about excesses in the City of London. People recognise that something is wrong when a banker earns in a week what a nurse earns in a year. The common ground goes beyond income and wealth - to issues of working time and the quality of our environment to where power lies in our society. The hidden injuries of an unresponsive state are as important as an over-powerful market. Unless we address these issues, we narrow our appeal - when it needs to be broad.
Third, real progress needs a movement as well as argument. Moving on from the idea that we win despite our party rather than because of it is essential. People join parties because of ideals and because they want to feel they have a voice. Centralisation, diktat, managerialism - all are routes to a hollowed-out party and an unsuccessful movement.
The movement matters because it builds electoral support. We will succeed in making the case for equality only if we have not just a political party with hundreds of thousands of members, but a genuine movement that reaches out beyond this. However, the movement doesn't make change happen just by helping to win elections. Political change happens not just through legislation and government policy. We need to be the allies of those who make change happen - those like London Citizens, which has brought about change on the living wage through popular pressure; the trade union movement, fighting for better terms and condition; and like the environmental movement, through projects like Transition Towns.
A story of us
Finally, we need to learn the lesson that politics must inspire people with a view about our country and what it can be. Doing better for yourself and your family must be an essential part of Labour's appeal. But a story of us - as a country - is also essential. David Cameron's big political project is based on a shrinking of the state. He tells us nothing stirring about what our nation can become. I believe that the brief interest in Nick Clegg at the last election shows that people are yearning for something more.
We must inspire people that there is a fairer, more equal, more just society that a refounded Labour can offer. People want a society where we each make our contribution, where we care for each other, where we treat each other with respect and dignity. We should be optimistic that, with the right leadership, appealing to head and to heart, we can stir the sense that politics matters and that idealism can appeal. That we can all be proud to be part of a more equal country: healthier, happier and more secure.
Ed Miliband is the MP for Doncaster North (Labour) and shadow energy secretary