A platitude in the mouth of a clever man can be profound. Phrases such as “all men are created equal”, “the greatest happiness of the greatest number” and even “tough on crime, tough on the causes of crime” may sound too glib to have meaning, let alone effect. But they can, on the contrary, produce important consequences.

David Cameron’s “it’s time we focused not just on GDP but on GWB — General Well-Being” may be the most trite idea of all. Nonetheless it could alter the nature of British politics.

It suggests a new direction. Since the late 19th century, when the majority of male adults got the vote, economic improvement has been the main preoccupation of politicians. Whether they promised more for everybody or a “fairer” distribution of existing wealth, the electoral bribe of material enrichment was assumed to work with voters.

Of course MPs have always known that other things matter, too. Housing and transport became important policy issues in the 19th century and education and health in the 20th century. But the pre-eminence of an economic policy, directed towards growth or redistribution or both, has never been seriously questioned.

Cameron’s principal objective in making the speech was once more to challenge voters’ stereotype of the Conservatives. He believes, rightly, that the public still associates his party with the “loadsamoney” 1980s when, supposedly, Margaret Thatcher brought about a society of greed and rampant individualism.

Her idea was in fact quite different. Because she had been brought up to believe in duty she assumed that those who got rich would recognise their obligation to help others and that would create a much healthier society than one in which the state was the only fount of charity.

People have personal duties, she thought, that cannot be subcontracted because society is only what the people who compose it make it. That is what she meant by “there is no such thing as society”.

So while Cameron appears to make a clean break with discredited Thatcherism, it is far from being the U-turn that it appears.

Nor should it be surprising if the Conservatives claim to be less obsessed with growth than Labour. It was Karl Marx who asserted that man was motivated by economics. Tories traditionally believed in many things other than greed or growth: in God, the countryside, patrician duty and the virtue of philanthropy. In modern times the party eulogised the family. Cameron has found a way to laud the joys of parenthood without evoking 1950s images of housewives armed with vacuum cleaners.

We should not exaggerate what has just happened. Cameron was suggesting that we (or he) should focus “not just on GDP”, which is of course different from “not on GDP”. He is not going to tell us at the next election that growth does not matter. But he may say that some growth should be sacrificed (for example to counter global warming) and that other things matter more.

That opens the way not only for politicians to promise different things from in the past but also to promise less overall.

They have fallen far behind the public in their understanding of what politics can achieve and therefore what politics is for. Voters perceive how puny their political masters have become. Nation states have only limited success in stemming the rise in oil prices, reducing carbon dioxide emissions, countering bird flu or even defeating terrorism. Central bank governors influence economic policy more than ministers of finance. In Britain government policy has only a limited impact on the health service or schools even though those sectors are nationalised. The state is palpably incompetent to run the prison and immigration services.

Yet the promising has gone on. Politicians commit themselves to utopian improvements that the public knows they will not deliver. It is one reason why people feel contemptuous of the political process.

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