A year or so back, while walking in Oxfordshire, the Leader of Her Majesty's Opposition found himself staring at a dry-stone wall and being asked to contemplate the future of Conservatism.

His companion did not ask him to kick the stones, copying Samuel Johnson's refutation of Bishop Berkeley on the non-existence of matter. He asked him merely to look at how the wall was constructed. And in looking, understand the new thinking - exciting and different - that might shape a Cameron government.

Tonight the London School of Economics will be the venue of an important event: an audacious attempt by the Conservative Party's leading intellectual to relate a new Tory narrative. After decades in which his gang has been seen as purely the economics party, David Willetts is going to try to pick his colleagues up and put them down in a new place.

The Oakshott Lecture is the fruit of 15 years' thinking by Mr Willetts. It began with his book Modern Conservatism in 1992 and continued with his pamphlet Civic Conservatism. He wrote of the need for his party to have more to say about community and social cohesion and fairness. But in those days the Tory market for his ideas was smaller. One party leader carried an underlined copy of Civic Conservatism in his pocket and brandished it in conversations, but that leader was Tony Blair.

Now Tories are listening more attentively. They need to. David Cameron has talked of his party being for quality of life, not just quantity of money, and has asserted confidently that Conservatives now accept that there is such a thing as society. But where are the ideas that can justify these claims? Are they distinctively Conservative or simply a capitulation to the ideas of the Left?

Even the tools that Mr Willetts intends to use are novel. For 30 years the most interesting ideas for Conservatives have come from economists. Now it is being proposed that sociobiology, game theory and social psychology power the Tory agenda. Alongside well-known thinkers such as Milton Friedman and Friedrich von Hayek, new names are being bandied about - Robert Axelrod, E.O.Wilson, John Nash, Ken Binmore and others.

The starting point of the argument is, ambitiously enough, the starting point of life. The sociobiologists argue that our minds and our behaviour - not just our bodies - are the products of evolution. That behaviour that made us fitter in an evolutionary sense has been selected over that which did not. This was an immensely controversial theory when first proposed, but over the past 20 years has won out over its critics.

What's new for Tories about that? Isn't this just the sort of crude winner-takes-all, dog-eat-dog, social Darwinism people associate with them? No. And that is where game theory comes into it.

Game theory uses maths and logic to analyse how people should respond to the choices of others. The most famous piece of game theory is the prisoner's dilemma. Two prisoners, separated from each other, are asked to choose between confessing and staying silent. If one confesses and his partner-in-crime stays silent, the confessor gets off scot-free, the other a ten-year sentence. If both stay silent they each get a token one-year sentence. If both confess they get nine years each.

What should they do? The maths is clear. They should both confess. But game theory introduces a twist. If the prisoner's dilemma is repeated over and over again, it can make sense to co-operate - for instance you don't betray until you are betrayed. In other words, game theory shows that co-operation is a natural and successful evolutionary strategy for individuals in circumstances where they have repeated interactions with others, or believe they might have.

This bit of maths explains observations made by biologists. Vampire bats, for instance, feed other bats with extra blood they have collected, even though those others are not related genetically. They expect the same favour in return on another day. This behaviour is known as reciprocal altruism - self-interested and interested in others at the same time.

And we know that it is hard-wired into human behaviour because of the work of social psychologists. Any number of experiments show how easily the response can be triggered. A Hare Krishna devotee presses an unwanted flower into your hand and you are more likely to donate, despite yourself.

What does all this suggest politically? That Tories should design institutions that encourage reciprocal altruism. A dry-stone wall, like the one David Willetts pointed out to David Cameron, does not have any glue or cement holding it together. It holds together because of the way it has been designed.

Similarly, the aim of Tories is not to pour social glue on civil society through public policy, and armies of new laws, nor is to enunciate some new abstract principle of justice that might be at variance with human nature. It is to help society find different kinds of equilibrium.

This new thinking justifies the Tory preference for decentralisation, favouring smaller, independent institutions in the public sector. It explains why you might want schools, say, small enough for pupils and teachers to know each other properly. And hospitals that care about their own reputation and not just the amorphous NHS ethos.

It also explains why the new Tories might want to cut inheritance tax. Traditional free-market thinking rather approves of taxing “unearned income”. Reciprocal altruism shows that such income plays an important social role.

Mr Willetts's lecture leaves questions unanswered and a huge amount of heavy lifting still to do. But I wouldn't be all that surprised if, when the history of David Cameron comes to be written, the subject of vampire bats features prominently.

daniel.finkelstein@thetimes.co.uk

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