When political parties run out of ideas they ossify; when governments do it they die. When governing parties leach out their intellectual lifeblood, opposition parties grow in confidence. It’s a zero sum game. You saw it in the 1970s, with Callaghan’s exhausted, lacklustre government. Thatcher’s party fizzed with free market ideas, fuelled by rightwing thinktanks: the Adam Smith Institute, Centre for Policy Studies and the Institute for Economic Affairs. On the eve of her election victory in 1979, Margaret Thatcher said: ‘We have accomplished the revival of the philosophy and principles of a free society, and the acceptance of it. And that is absolutely the thing that I live for.’ It was an animating philosophy which sustained the Tories for over a decade. Labour, as Tony Blair later commented, ‘lost its intellectual self-confidence under the onslaught of the Thatcherite right’.

You saw it again in the mid-1990s. John Major’s government threw away its claim to economic competence on 16 September 1992, when it splurged £3.4bn shoring up sterling, before Britain was ejected from the exchange rate mechanism. After that, the Tories’ intellectual locker was empty. Their 1997 manifesto promised to cut public spending below 40% of GDP, a goal of 2.5 per cent inflation, to raise the threshold of inheritance tax, more grammar schools, to keep Britain out of the social chapter and 2,500 more nurses over five years (Labour has delivered over 80,000 more nurses). The Tory manifesto, like the Tory government, was reactionary, out-dated and out of step.

New Labour dusted down its traditional ethical socialism and applied it to the modern age. The rewriting of Clause IV did not ditch socialism, but renewed it. Tony Wright in his Socialisms described a process of ‘theoretical reconstruction’ which succeeded in ‘converting socialism into social-ism, and constructing a liberal communitarianism anchored in a broad intellectual inheritance of the left centre’. The left-leaning thinktanks – IPPR and the Fabians – and the pressure groups such as Progress were buzzing with ideas and awash with new policies.

If you believed the story being told by most of the media that Labour has lost the 2010 election, and the Tories are on the brink of office, you would expect history to be repeating itself. Labour would be intellectually bankrupt, and the Tories would be rich with policy. The past few weeks have proved that the Tories’ policy agenda is as confused as a chameleon on a packet of Sobranie Cocktails. Has the Tories’ policy shambles been mirrored by Labour’s growing policy strength? The publication of a new collection of 10 essays by leading leftwing thinkers and academics, edited by James Purnell and Graeme Cooke, suggests the answer is yes.

Purnell has dedicated much of his time since resigning from the cabinet last year on the Open Left project at Demos, which seeks to answer the question ‘what does it mean to be on the left today?’ These essays – We Mean Power: ideas for the future of the left – try to answer some of the fundamental questions for socialists, from equality to citizenship.

They provide three reasons to be cheerful. The first is that it encouraging that the writers – unlike the Bennites in the early-80s who clambered over the government’s still-twitching corpse – don’t try to define socialism by distancing it from Labour’s record in office. Sure, there’s a hard-headed assessment of New Labour’s failings: failure to properly prioritise our objectives, or to adequately modernise our democracy (Meg Russell suggests that Labour’s enthusiasm for radical constitutional reform had dissipated by the 1920s), or to explain our purpose properly to the public. But this is not the blame-storm of a party in terminal decline.

The second reason to be cheerful is that the essays are rooted in the intellectual tradition of British socialism. It’s a reminder that we stand on the shoulders of giants: ethical socialists such as Richard Tawney, decentralisers such as GDH Cole, radicals such as TH Green, Hobhouse and JS Mill, and modern-day guiding lights such as Amartya Sen and John Rawls. Buffeted by the crises in our democracy and economy, we need our ideological anchors as never before.

The third reason is that these essays, and the rest of ferment of ideas on the modern left, suggest that Labour has the confidence to go into the election with a serious policy offer for a fourth term. We have the unprecedented opportunity to present a manifesto which speaks to the public’s desire for reforms of the financial system, the public services and the constitution. Unlike the Tories’ vacuity in 1997, Labour’s 2010 manifesto should be more radical than those in 1997, 2001 or 2005. The crisis should be the catalyst for reform, not the excuse for safety first.

Ideas don’t win elections. A party’s success is a heady cocktail of credible candidates, trusted leaders, eye-catching policies, and energetic communications, mixed with a large measure of good fortune. But without a sound ideological underpinning, all the election posters, leaflets, speeches, broadcasts and canvassing are pointless and ritualistic, and after a while the voters spot that you are talking loud but saying nothing.

Just ask David Cameron.