Yes, I know, the question has been asked repeatedly over the past few years -- but I'm afraid it's time to ask it again.

As my colleague Mark Mardell, the BBC's North America editor, put it in a blogpost a couple of days ago: "The drumbeat of war has grown louder in the past few days."

That drumbeat emanates from Israel, where the defence minister, Ehud Barak, talks of Iran soon entering a "zone of immunity", in other words a moment when its uranium enrichment programme will be so well protected in deep underground bunkers that it will become virtually impregnable.

According to the Washington Post, the US defence secretary Leon Panetta "believes there is a strong likelihood that Israel will strike Iran in April, May or June ... Very soon, the Israelis fear, the Iranians will have stored enough enriched uranium in deep underground facilities to make a weapon -- and only the United States could then stop them militarily."

And the New York Times reported this week: "Amid mounting tensions over whether Israel will carry out a military strike against Iran's nuclear program, the United States and Israel remain at odds over a fundamental question: whether Iran's crucial nuclear facilities are about to become impregnable."

Yes, says Mr Barak; No, say the Americans. The Washington view is that the ever tighter sanctions imposed on Iran are having a real effect, so the best policy is to let them bite harder. The Israelis say they can't risk waiting much longer.

For several decades now, a vital element in Israel's security strategy has been its status as the only nuclear power in the Middle East. (It has never admitted as much, but it's perfectly happy for everyone else to say so.)

But if Iran were to become the region's second nuclear-capable power, that invaluable strategic superiority would be wiped out at a stroke. Israel would, in theory, then itself be vulnerable to a nuclear attack.

Iran, of course, sees things exactly the other way round. It has had nuclear ambitions since the days of the Shah, and no Iranian politician, not even the reformists like Mir-Hussein Moussavi, is prepared to give up Iran's right to develop a nuclear programme, officially solely for peaceful use.

Iranians remember a glorious past when the Persian empire stretched right across the region and included what is now Israel. (Just a few days ago, the deputy Israeli prime minister Silvan Shalom said he believes Iran is now trying to revive that former empire.)
But imagine you were an Iranian strategic planner. You have recently gained valuable extra regional influence with the US-engineered overthrow of your old enemy Saddam Hussein in neighbouring Iraq, and the installation in Baghdad of a much more friendly, Shia-dominated government.

But to your west, the signs are a lot less encouraging. Your long-time allies in Syria are in deep trouble, and if they are defeated, their place will be taken by a Sunni-dominated administation with no great love for Tehran.

Coming after a string of Arab upheavals that have vastly increased the influence of the Sunni Muslim Brotherhood across the region (aided and abetted by the unimaginably wealthy Qataris), the overthrow of the Assad dynasty in Damascus would be extremely bad news.

So, as you analyse the rapidly shifting power relationships, would you be in the mood to give up a nuclear programme that earns you the attention -- and yes, the fear too -- of your neighbours?

Iran's leaders are not, as the Americans would say, in a good place. The man in charge, the supreme leader Ayatollah Ali Khamenei, is elderly and said to be in poor health. He has fallen out with the president, Mahmoud Ahmadinejad, who is now said to wield little real power.

The economy is in a mess, and many poorer Iranians are finding it increasingly difficult to make ends meet. Uncertainty beyond the country's borders is matched by growing restiveness at home.

According to the Washington Post: "US officials don't think that [Israeli prime minister] Netanyahu has made a final decision to attack, and they note that top Israeli intelligence officials remain sceptical of the project. But senior Americans doubt that the Israelis are bluffing. They're worrying about the guns of spring -- and the unintended consequences."

Do the names Ian Sartorius-Jones and Gajbahadur Gurung mean anything to you?

Probably not, unless you knew them or their families personally -- but they both died in Afghanistan last week while serving with the British army.

They were the 396th and 397th British service personnel to die in Afghanistan since the anti-Taliban invasion of 2001 -- so the likelihood is that within the next few weeks, the death toll will reach 400.

Now cast your mind back to June 2010. That's when the British military death toll in Afghanistan reached 300. David Cameron had been prime minister for barely a month, and he said this: "We are paying a high price for keeping our country safe, for making our world a safer place, and we should keep asking why we are there and how long we must be there."

What do you think he meant by the words "keeping our country safe ... making our world a safer place"?

This is what I think he meant: defeating the Taliban and al-Qaeda, or at the very least weakening them to such an extent that they pose only a minimal threat.

But now consider that leaked NATO report, based on interviews with thousands of alleged Taliban detainees, which made the headlines this week: "Afghan civilians frequently prefer Taliban governance over the Afghan government, usually as a result of government corruption."

What's more, it suggested there has been "unprecedented interest, even from members of the Afghan government, in joining the Taliban cause."

If you were listening to the programme on Wednesday evening, you'll have heard the former Afghan presidential candidate Ashraf Ghani and the Conservative MP Rory Stewart both agreeing that the only hope for the future of the country is to bring at least some of the Taliban back into the mainstream political process.

In which case, if you were the parent or relative of a member of the British armed forces in Afghanistan, you might be tempted to ask: "Excuse me, Mr Cameron, if the Taliban are on their way back anyway, why exactly are we still sending servicemen and women into harm's way?"

The current plan is for "substantial numbers" of British troops to start withdrawing from Afghanistan next year, and for all combat troops to be gone by the end of 2014. The word yesterday from Downing Street was that the 9,000-strong UK contingent will have ended their lead combat role by the end of next year.

And the Americans are now signalling that they hope to have had made a transition from combat to training and advice by the end of next year as well -- that's rather sooner than they'd previously envisaged -- with more than 20,000 of the current 99,000 US troops in the country having returned home by the end of 2013.

So here's the picture: by the end of next year, substantial numbers of US and British troops will have left Afghanistan. And Taliban commanders, in the words of the leaked NATO report, "increasingly believe their control of Afghanistan is inevitable."

Their confidence may, of course, be misplaced. And it is certainly arguable that by maintaining military pressure on them, the US and its allies will make the Taliban more prepared to engage in a genuine political dialogue.

Meanwhile, there's still the Pakistan issue to be dealt with -- to quote that NATO report again: "Reflections from detainees indicate that Pakistan's manipulation of Taliban senior leadership continues unabated."

Pakistani officials repeatedly deny that they maintain close covert links with the Taliban, but Western intelligence agencies are convinced that, as David Cameron put it 18 months ago, Islamabad is "looking both ways" in the fight against terrorism.

Perhaps it's worth bearing this in mind, though. When Pakistani officials talk of the Taliban, they're thinking principally of the Pakistani Taliban, not the Afghan variety. (Taliban, by the way, simply means students, a reflection of the movement's origins in the religious schools, or madrassas, that were attended by tens of thousands of Afghan refugees who fled to Pakistan after the Soviet invasion of 1979.)

The Afghan Taliban, if the Western spooks are right, are largely guided and run by Pakistani military intelligence. Their Pakistani namesakes, on the other hand, devote much of their time to attacking that same Pakistani military.

According to a New York Times analysis: "They share an ideology and a dominant Pashtun ethnicity, but they have such different histories, structures and goals that the common name may be more misleading than illuminating."

None of which, I suspect, will be of much comfort to the British troops on the front line.

When I was at school, long, long ago, I studied a subject called English literature.

And when I was old enough to get my first passport, it was issued on behalf of a country called the United Kingdom of Great Britain and Northern Ireland. The word England, or English, didn't appear anywhere.

How much simpler it would have been if I'd been born in France, or Germany: French literature, French passport; German literature, German passport.

As far as I know, there's no such thing as "British literature", and there's certainly no "United Kingdom literature".

(Of course, English is a language as well as a national and cultural identity -- which is why we can also study American literature, or African literature, written in the same language but from a very different cultural background.)

So do labels matter? I suspect they do, because they help us describe who we are, who we feel ourselves to be. And surely that's an important part of the newly-invigorated debate over Scottish independence.

I've yet to meet a Scot who doesn't bristle indignantly when some ignorant foreigner describes them as "English". To be Scottish, or indeed Welsh or Irish, is, in part, to be not-English -- and perhaps we not-Scots need to recognise that more than we sometimes do.

Incidentally, while we're on the subject of national identities, I'm reminded of how the author and Anglican priest William Inge, who served as dean of St Paul's a century ago, defined what constitutes a nation: it is, he said, "a society united by a delusion about its ancestry and by common hatred of its neighbours."

Alex Salmond, Scotland's first minister, is going to great lengths these days to say that he's not an England-hater. Far from it, he says: he wants Scotland to be a good neighbour to England instead of a surly tenant -- and a confident, independent Scotland would help England to become equally confident, equally independent.

For now, all the opinion polls suggest that he has not yet convinced a majority of Scots that going it alone would be in their best interests. If he held an independence referendum tomorrow, he'd probably lose. Indeed, there seem to be more people in England than in Scotland who would be happy to see the two nations cut the ties that bind them.

If we look around the world, we can find other examples of countries that have split up, and we can choose which one to focus on, depending on what point we want to prove.

Czechoslovakia? The "velvet divorce" of 1993 -- Generally speaking, a success.

Ethiopia? The independence of Eritrea, also in 1993 -- Not a success at all, leading to continued conflict over borders and thousands of deaths.

Serbia/Kosovo? The unilateral declaration of Kosovan independence, 2008 -- a highly controversial example, of course, as it was done without the agreement, indeed, against the furious opposition, of Serbia. Not how it would happen if Scotland were to vote for independence.

But here's one aspect of the debate that perhaps hasn't yet received as much attention as it should. If the Scots want to feel more Scottish, and the English want to feel more English, where does that leave the people who insist that they really do feel British, rather than Scottish, English, Welsh, or Irish?

What about the child of immigrants from Cyprus, born here, English as first language, UK passport -- British, yes, but English?

Or the grand-child of immigrants from Jamaica, or India -- British, yes, but English?
(Declaration of interest: I am myself the child of refugees.)

National identity is tricky in a world of mass migration -- but it's going to be a fascinating debate.