Iran stands on a precipice. The opposition demonstrators have lost all their old fear of the authorities, as the escalating protests of recent days show. But the regime shows no sign of giving in either. An unstoppable force meets an immovable object.
What the ultimate result of this clash is, and how it will unfold chronologically, no one can predict with any accuracy, though it seems that the writing may be on the wall for the men in power in Tehran.
What we do know, meanwhile, because the authorities have confirmed it, is that at least eight people died in a series of clashes in the capital and elsewhere, which erupted following the death of a prominent opposition cleric.
The official death toll is almost certainly a considerable understatement, which means the burgeoning pro-democracy movement in Iran already has a fairly lengthy roll call of martyrs.
Spilled blood is a powerful and energising symbol in any country. It is especially so in Iran, where there are strong memories of the police shootings that became the catalyst for the final push to overthrow the Shah.
The government knows this all too well – hence its relative restraint in using force to contain the protesters until now. The arrest yesterday of several aides to the opposition leader Mirhossein Mousavi – whose nephew was among those shot dead on Sunday – may mark the beginning of a much tougher course in coming days. If the gloves come off, things could turn bloody indeed, for one factor that has really emerged in recent days is the mutual hatred that now exists between the regime and its disparate foes.
For us, standing on the outside and looking in, there are feelings of anguish and helplessness. The sympathies of almost all of us lie with those who, to borrow from the events of the 1960s in Czechoslovakia, would like to see a "Tehran spring"; an Islamic regime, perhaps, but with a more human face.
President Ahmadinejad, meanwhile, has forfeited his claims to legitimacy as head of state, having benefited from what everyone suspects was a falsified election result in June.
Now he clings on to his high office, decked out in the rags of ultra-nationalism and irresponsibly courting collision with the US and Israel with belligerent grandstanding over nuclear power and even more belligerent rhetoric about annihilating Israel. Posing as the great patriot, his claim to be defending his embattled country against a coalition of Zionists and imperialists is his only remaining card.
We must bear that in mind when considering what our own governments should do in response to what may be a protracted, possibly agonising, struggle between Ahmadinejad and the Supreme Leader Ali Khamenei on one hand, and the alliance of clerical reformers and more secular-minded liberals on the other.
We must recognise that there is nothing anyone outside Iran can actually do physically in this situation to assist the opposition. This isn't Kosovo, a postage-stamp-sized land in Europe's own backyard that Nato can handle with a little air power.
All we can do, in fact, is talk; that is, offer verbal support to those who, whatever their agendas, seem a lot more democratically minded than their opponents. Even in the realm of talk, however, we must be careful not to provide President Ahmadinejad with a pretext for claiming that Western powers are trying to meddle in Iran's internal affairs. For now, silence may be the best course.