Anthony Seldon: The politics of optimism will be the defining theme of our century

Steve Hilton, David Cameron's influential policy adviser, was glued to the television when Ed Miliband delivered his leader's speech on Tuesday afternoon.

One portion made him jump: "We are the optimists in politics today." For years, Hilton had been banging the optimist drum and, until the banking crisis, he had been carrying all before him. Cameron had even started speaking about Britain following Bhutan in being interested in measuring "general well-being" (GWB) alongside gross domestic product (GDP).

Hilton, more than any other influential figure in politics today, understands the agenda which will come to dominate 21st-century politics – that the quality of life matters as much as quantity and metrics. An obsession with the latter is destroying so much that is good about our society. One has to only look at our schools to see that the fixation with exam results and league tables has come at the cost of joy of learning, and our young are the losers from it.

Cameron's "Big Society" embodies much of the thinking of the optimistic approach. Following the Swiss philosopher Rousseau, it has a benign view of human nature, believing that individuals are naturally good and will want to look after others and improve their communities if the deadening hand of government is removed. It is the opposite of the Hobbesian approach which still bedevils the right wing – that you can't trust people to do the right thing, especially not if they're working class, so you need the state to watch over them. Trust is the key. All politicians talk about it. But it is just talk.

The danger of the "Big Society" approach is exactly the opposite of what many Conservatives fear: not that it will be too important, but that it will not be central enough in the agenda of the Coalition Government. The worry is that George Osborne and the humourless grey people who influence him in politics will be insensitive in the spending review, and create cycles of pessimism to reverberate around the country.

Optimism is not the enemy of realism. Great leaders are optimists because they offer a vision of the future. Optimism is self-fulfilling, especially when tempered by realism. Optimistic leaders are more successful in making enduring change. Optimists bring out the best in those below them. They do so, not through fear, but by painting a picture of a brighter future, and the role of each in achieving it.

Positivity has received a series of assaults in recent months, some good, as with Barbara Ehrenreich in her polemic Smile or Die. There is indeed much that is superficial, mischievous and plain wrong about the "positivity" industry: sadness is inevitable and indeed can be ennobling and much positivity tries to sweep over reality with a glib glean. But some professional debunkers belittle what is valuable.

The Buddha, Aristotle and Confucius all had important contributions to make about optimism. In the contemporary era, the figure who has done most to underpin it has been Professor Martin Seligman, the American psychologist and authority on depression. In 1998, when president of the American Psychological Association, he asked why so much of academic psychology was concerned with aberration and mental illness, with psychosis and neurosis. He asked where were the corresponding studies that looked at the ingredients of a fulfilling life, successful relationships and flourishing organisations. Out of his inquiry was born the academic field of positive psychology which has made such a powerful impact over the past 12 years. Indeed, below the radar screen last week, Seligman was in town talking to top-level politicians and officials.

This thinking about optimism has helped us to understand much more how to enhance individual happiness and reduce unwanted misery. A concentration on self lies at the heart of the problem: "If you want to feel good, do good," says Tal Ben-Shahar of Harvard University. The work has made a significant difference to thinking about relationships. The traditional "marriage guidance" approach was for a third party to ask where a relationship was going wrong: the positive method is to ask where the relationship is going right, and to see what can be done for such occasions to grow.

What can be learnt from all of this about government policy? David Cameron will be unveiling his new agenda for the Coalition Government next week, and he should extend the Big Society to embrace the following:

"Positive health" policies put the focus decisively on preventing illness rather than, as the NHS still currently does, spend billions coming to the aid of people who are suffering from avoidable illnesses. The surgeon Ara Darzi understood this better than anyone; he was a non-political minister under Gordon Brown and needs to be listened to far more now. It is utterly bizarre that we accept illness and do so little to educate and socialise people into good health.

"Positive education" stands education on its head as, currently configured, schools twist and contort what they do to produce exam results. Quite what these exams are for no one is certain, but as long as they're there and being closely monitored, heads have to dance to their tune. But schools should be about a "leading out" of each child's unique talents and abilities, in all their eight different aptitudes and intelligences. It should be about preparing them to lead meaningful and productive adult lives. The increase in child mental illness, alcohol abuse and violence shows all is not well. Something has to be wrong when life in Britain, which has never been better materially, sees 31 million prescriptions for antidepressants annually.

Universities are losing their way: underfunded and overly controlled, they have lost touch with their mission to be liberating the mind and spirit in an experience which students should value as a profound privilege. A positive university policy begins with asking "what are universities for?". At present, many students, academics and university administrators do not know. They have even stopped asking the question.

"Positive policing" is about deterring crime. It is insane not to have community police. Every good teacher knows that the aim is to stop bad behaviour occurring, not to investigate and punish it once it has. But that is what police do, and criminals are then banged up in prison – the Nobel Prize winner for the most counterproductive of all institutions.

Transport is an area neglected by successive British governments. "Positive transport" policies begin by asking "why travel?", and how to make it as efficient, attractive and environmentally friendly as possible.

"Positive employment" policy ensures that the workplace is a delight and brings out the best in workers. It uses volunteering to combat unemployment, which is so destructive of morale, health and sanity.

This optimistic agenda will become dominant in the 21st century. Nick Clegg squandered it last week while Ed Miliband talked it up this week. Now Cameron has the chance to show that he is capable of leading optimistically again.

Anthony Seldon's book 'Brown at 10' is published in November