There is a wistful misconception that actresses are all spiritual descendants of the vivacious Lillie Langtry. But on the contrary, the more beautiful and sexy a modern actress is, the more solemn she is likely to be.
In the current Harper's Bazaar, Jane Birkin is asked for recommendations to get us through December.
She suggests we visit sewers and think harder about Burma.
The Amartya Sen of actresses is Angelina Jolie.
Why the surprise that she has written an article for The Economist on the troubles of Darfur? She has already stiffened The New York Times's op-ed pages on the subject. She pitches up at the World Economic Forum at Davos, along with Sharon Stone, something of a Noam Chomsky in her own right. It can only be a matter of time before Gordon Brown invites Jolie into his tent.
Certainly Brown's thundering over the situation of Darfur is in line with Jolie's own concerns. Is she writing his speeches already? Remember Brown's rousing challenge: "We have sent a message to the Government of Sudan. And we will not rest until there is an end."
Does this not echo Jolie's writing? "This might be the moment to stop the cycle of violence and end our tolerance for crimes against humanity."
Beautiful and blazing as she is, Jolie's appearances in the geo-political Press irritate some people. Her critics argue - in homage to Norman Mailer - that her fondness for clichés ('cycle of violence', 'cycle of violence') diminishes her case.
They accuse her of being naïve. What exactly are we supposed to do to stop the cycle of violence, apart from wringing our hands?
Brown's moral fervour is subdued by his foreign policy speech last week to the Lord Mayor's Banquet, in which he promised to put British interests first. This puts an Atlantic ocean of blue water between him and his liberal interventionist predecessor.
Nobody condones the savagery of the Janjaweed, the raping of women, the displacement of two million people.
But neither is anyone keen to send their own soldiers to the Sudan to settle tribal warfare. Brown's confident proposals for a UN peace-keeping force to replace the ragged African Union one are stalling as the Sudanese Government proves choosy about outside interference.
It is shameful that Western countries are reluctant to donate helicopters and equipment.
And yet, and yet, the British are desperately short of Apache helicopters in Afghanistan, which is described as our front line against terror.
As David Miliband has learnt, the world is a far more complicated place than good intentions would like.
The safest definition of national interest is the narrowest.
This is why we need figures such as Angelina Jolie; she is an antidote to despair.
Of course there is something comic about grand Hollywood fundraising parties. Helen Fielding's first novel, Cause Celeb, satirised fundraising for Africa. It jars to see champagne and ballgowns, when you could vaccinate the whole of the Congo for the same price.
But Jolie coughs up her own money and she has proved tenacious.
Mariane Pearl, the widow of the murdered journalist Daniel Pearl, praised the actress who portrayed her.
"Celebrities are doing the work that journalists are not. We can't afford to be cynical about that," Pearl said.
Celebrities can be sanctimonious about global affairs and some of them are undeniably hard going - Bianca Jagger springs to mind. But if their luminously shocked faces spread across Hello! magazine tug at our consciences, they are a force for good.