A house of cards disintegrates in a gentle breeze; a structure built on proper foundations can withstand much greater shocks. The events of yesterday will test whether the Middle East peace process is solidly based or just another house of cards.
There is no doubt that the blast in Jerusalem was a substantial shock, not just literally but politically as well. It is a familiar ploy for hardline militants to seek to unsettle tentative efforts at compromise by a violent act.
Inevitably, especially where civilian casualties are involved, politics goes on hold for a time: if nothing else, human decency would require a pause.
Confusion reigned and the news at first was that the victims of the blast were the bombers themselves. Within an hour the story had changed: the victims were Israeli, possibly members of the ultra-orthodox Hasidic Jewish community in Jerusalem, many of whose members crowded around the scene in an angry mood.
It was not a good place or time to be an Arab, and there were reports that a Palestinian man had needed police protection.
The day began with hope and ended with anxiety. Despite the extremely robust - and frequently lethal - response to the Palestinian Intifada, it was clear that the Israelis wanted to salvage the peace process if they could do so without appearing in any way weak. Hence the visit by the 77year-old former prime minister, Mr Shimon Peres, to Gaza to meet Mr Yasser Arafat.
Dawn broke on a note of compromise. Statements would be issued by both sides. There were reports of Palestinian police restraining protesters and of Israeli tanks withdrawing from their positions at Palestinian towns and villages.
The question on everyone's mind was whether the Arafat leadership had sufficient influence with militant Palestinian youth to persuade them that peaceful protest was better than throwing stones.
Anyone who has watched the demonstrations here - and the astonishing sight of boys and even children challenging Israeli military might with catapults - would have to admit to a certain scepticism about Mr Arafat's ability to turn the violence off like a tap, which is what many Israelis claim he could do if he wanted. The next few days will show whether Mr Arafat has control over the brakes or just the steering.
Israeli sources said the tough tactics used against Palestinian demonstrators were intended to send a strong message, letting the rioters know that Israel was in charge and would not be backing down. But if they were intended to cow the Palestinians into submission, they have demonstrably failed. The teeming masses of Arab youths keep coming forward into the front line, and for every youngster who dies from a rubber bullet to the head or a high-velocity shot from a sniper's rifle, there seem to 10 to take his place. An Israeli hardliner told me that if these people wanted to commit suicide, that was their problem.
The Palestinians are less well armed than the Israelis, by a long way, but they have been adding to their store of weapons. More and more, what begins with stone throwing ends up in a gun battle.
Three Israeli soldiers were killed on Wednesday. The conflict appears to be intensifying, not tailing off.
The Arab League summit two weeks ago disappointed the militants with its largely verbal response to Israeli actions, but one wonders how long this posture can be maintained in the event of a prolonged continuation of violence.
The abject poverty and miserable living conditions of many Palestinians in refugee camps have to be seen to be believed. The West has ignored this problem for decades, so it is no wonder that Palestinian youths have begun to turn to extreme ideologies and desperate remedies for their plight.
Perhaps the peace process could still defuse the situation: Mr Arafat's prestige is substantial and he remains both father of his nation and its primary figurehead.
But the process has been stagnating for some time and the best-laid political schemes lose their credibility unless there is forward movement. There has been little dissent in Israel about the use of combat methods to resolve what many see as a policing problem. But there are clearly divisions between those who still see potential in a continuing arrangement with Mr Arafat and hardliners whose provocative actions seem calculated to kill all hope.
The extremists grow louder: how long can the centre hold?