By Brian Wheeler
BBC News politics reporter
It may, in the words of Ken Dodd, be the greatest gift that we possess.
Mr Cameron loves depressing rock music
But you rarely hear a British politician talking about it.
Politics at Westminster is all about targets, delivery, medium-term goals, statistics and pledges. Ministers talk about "life chances" and "opportunities" and people fulfilling their potential.
Ask them about the sum of human happiness - and if their policies add to it - and you are likely to receive a blank look.
But not, it seems, from Conservative leadership hopeful David Cameron.
In a lengthy speech last week, the 38-year-old frontbencher listed the benefits of education - it boosts social mobility, social cohesion and Britain's economic competitiveness.
"But it also matters crucially for a fourth reason," said Mr Cameron.
"It's one that, strangely, politicians don't talk about often enough. Happiness.
"I believe that education is one of the keys to happiness. Education that inspires and instils a love of books, of knowledge and of learning is one route to a happy and fulfilling life.
"You don't have to take Mill's side against Bentham in arguing that there are "higher forms of pleasure" to believe that loving learning is one way of loving life."
But the education spokesman, who says he relaxes by listening to "miserable" rock music such as The Smiths and Radiohead, is not the first senior Conservative in recent weeks to strike a more philosophical, even whimsical, note.
Oliver Letwin, freed from the bean-counting drudgery of the Treasury brief, breached another modern political taboo in one of his first speeches as the Conservatives' environment spokesman.
Addressing Iain Duncan Smith's Centre for Social Justice, Mr Letwin called for a new culture, in which politics is conducted "as if beauty matters".
Ken Dodd knew a thing or two about happiness
Mr Letwin said politicians could learn from the Make Poverty History campaign, which had touched a chord with the public and "created a political romance".
The removal of beauty from the political vocabulary is one reason why the environment debate had become "desiccated", he added, and why so many people dislike politics.
So, are they putting something in the water at Conservative Central Office? Or are we witnessing the birth of a new political discourse?
Times columnist and former Conservative MP Matthew Parris says it is refreshing to hear politicians use language that has not been culled from a staff training manual.
"I think it is excellent that the word happiness should re-enter political discourse. We are becoming a bit fed up with targets and pledges and vows - the politics of measurement.
"It is nice to hear someone using that word in British politics. David Cameron seems almost the first politician since the American constitution to do that."
Of course, Mr Letwin and Mr Cameron, both old Etonians, may simply be attempting to put some clear blue water between themselves and the more populist - or wilfully philistine depending on your point of view - elements on Labour's front bench.
To take one much-quoted example, Charles Clarke caused a stir in academic circles when he was education secretary by saying education for its own sake was "a bit dodgy".
"I don't mind there being some medievalists around for ornamental purposes, but there is no reason for the state to pay for them," Mr Clarke told a meeting at University College, Worcester.
Labour has, to be fair, made some attempts to lift the veil on the mysterious concept of happiness.
A 2002 Cabinet Office report "Life Satisfaction: the state of knowledge and implications for government", looked at the cash equivalents of different life events.
Among other things, it found getting married was the equivalent of a £72,000 pay rise, while splitting up with your partner was worth minus £132,000.
But depressingly for politicians, the report concluded British governments over the past 30 years have not, on balance, succeeded in making Britain a happier place.
Perhaps they are just not trying.