Why is there a slightly uneasy feeling of déjà vu hovering in the air?

What’s the big idea? That’s the question often asked of opposition parties as they make their pitch to the electorate. If voters are going to be persuaded that it’s “time for a change”, there has to be something of substance to change to.

In that context it was good to see Roberto Unger in London last week. And indeed he was everywhere – at the IPPR, at the RSA, at the Fabian Society, and at the LSE (you can hear his talk on Radio 4 tonight). I got to hear him speak at an informal session at the Fabians’ new(-ish) offices on Friday, and a highly stimulating (and challenging) hour it was too.

Unger’s presence in town created a degree of intellectual excitement. That’s a good thing. “One more heave” was never going to be enough to get Labour back into government, especially after what was a heavy defeat in May 2010. New ideas and fresh thinking are needed. And in the three years since Ed Miliband became Labour leader the names of several influential figures have become – temporarily at least – much better known. The late Herschel Grossman and his colleague Minseong Kim were the inspiration behind the producer/predator theme that featured in Miliband’s 2011 conference speech. Maurice Glasman introduced us to “Blue Labour”. The Australian writer Tim Soutphommasane (profiled here by the New Statesman’s George Eaton) influenced Labour thinking on national identity and patriotism. Yale’s Jacob Hacker gave us “predistribution” and, unusually, seemed able to explain in quite simple language what it means. And now many have developed “a hunger for Unger”.

It’s all good. So why is there a slightly uneasy feeling of déjà vu hovering in the air? I think back to 1994-96, when once again the Labour leadership’s appetite for big ideas seemed pretty healthy. A loose network called Nexus was formed to connect thinkers with the New Labour leadership. Amitai Etzioni’s communitarianism was much discussed, for a while. Will Hutton’s “stakeholder capitalism”, as described in his best-selling The State We’re In, was briefly going to be the animating force behind a new Labour government. Tony Giddens’ “third way” remained a useful label – at least – for some time. But come May 2^nd 1997 the practical business of government, and necessary compromises, took priority. The big idea became getting things done. By the turn of the century intellectuals and their deep thoughts were less prominent. Instead, we had the Millennium Dome.

David Cameron has plotted a similar course, from the enthusiasm for a Big Society, with sunshine and well-being for all, to the harshness of the permanently leaner state he described in his Guildhall speech last week. His former speechwriter Ian Birrell suggested in the Guardian that the prime minister might benefit from taking another look at those earlier speeches. In vain, I fear. As big ideas go the Big Society was pretty flimsy, but even that has been binned. It was a notion conceived in sunnier times that could not survive contact with austere reality.

For what it’s worth, I was not really convinced by Roberto Unger’s arguments last week. His call for experimentation and devolution of power was interesting. But I was not sure that his vision of the state was completely practical, nor something that could or would win popular support. No matter: his challenge to politicians to show some imagination and find new solutions was an important one.

No-one would criticise Ed Miliband for being uninterested in ideas. With 18 months to go to the election more serious thinking is required to flesh out what this One Nation, predistributing, middle-out Labour government would look like. But governing is clearly a practical business, as well as an intellectual one. As the management guru Peter Drucker once said: “Plans are only good intentions unless they immediately degenerate into hard work.” Good, effective government is the biggest idea of all – and the hardest one to pull off.