Power is a funny thing, isn't it? You can't see it, touch it, or smell it - but you know soon enough if it's not there.
So does Gordon Brown have power? In theory, of course he does. He's the Prime Minister. But just look at what he's been forced into over the past few days.
Settlement rules for Gurkhas? Defeated. New plan for MPs' attendance allowances? Deferred. Titan super-prisons? Abandoned. National database? Ditto.
There was a terrible moment on Wednesday, right at the end of Prime Minister's Questions. It had been a rough old session, and the PM couldn't wait to get out of the chamber. As soon as it was over, he bundled up his papers and headed for the exit.
Then the Speaker announced: "Statement on Afghanistan: the Prime Minister." To jeers from the opposition, Mr Brown turned on his heels and made his way back to the dispatch box. He'd clean forgotten that he had more business to attend to.
So let's take it as read that, in the elegantly understated words of Peter Mandelson, "it's been a bit of a week." David Blunkett said as much this morning: his message to the government, put blunty, was: "Pull yourselves together."
But the question is this: Is it simply one of those Westminster squalls, that gets everyone in the village all over-excited and shiny-eyed? Or are we witnessing the slow but now certain disintegration of the Brown premiership?
I'll leave the prognosticating to the ³ÉÈËÂÛ̳'s estimable political editor Nick Robinson and his Westminster colleagues. But I have been thinking back a bit.
Who remembers Alec Douglas-Home? He took over as Prime Minister when Harold Macmillan resigned in October 1963, and was defeated in the general election of October 1964.
James Callaghan? Took over when Harold Wilson resigned in April 1976, defeated in the general election of May 1979.
John Major? Ah yes, John Major. Took over when Margaret Thatcher resigned in November 1990, won a general election in 1992, and stayed in office until he was defeated by Tony Blair in May 1997.
So Mr Major was the exception, even if his 1992 election victory seemed both at the time and thereafter to be an aberration. For much of the following five years, he gave the impression, in the words of his one-time chancellor Norman Lamont, of being in office but not in power.
Gordon Brown knows his history. He knows all this much better than I do. That's why, I suspect, he was so tempted to call an election in the autumn of 2007. He knew that with a mandate of his own, he'd have real, lasting authority. But he bottled it.
So his backbenchers no longer do his bidding. The chairman of the Committee on Standards in Public Life ignores his wishes. The president of Pakistan cancels a joint press conference with him.
In June, there are local and European parliament elections. I do not expect joyous results for the Labour party. In July, the full details of MPs' expense claims will be published, and the Westminster rumour mill is already churning red-hot with talk of forced resignations and by-elections.
On the other hand ... there are some little green shoots appearing across the Atlantic. US consumer spending was up 2.2 per cent in the first three months of this year; savings were up as well, and prices rose by 2.9 per cent year on year. In the current economic climate, that all counts as good news.
And if the US recession is bottoming out, it may just be that we won't be far behind.
Even so, if you were to ask me to bet on Mr Brown still being Prime Minister this time next year, I think I'd plead extreme poverty and head for the door.
Oh, and by the way, the says we shouldn't call it "swine flu" any more. It's "influenza A (H1N1)". What's wrong with the "new flu virus"?