The PLO leader Yasser Arafat's closest adviser speaks eloquently, fearfully, of this option. His remaining optimism is almost as brave as his ability to fear the worst.
Management consultant, publisher, philatelist, Mr Shaath is having to contemplate failure ever more frequently. "The peace process is in deep trouble," he says. "And if it collapses, what will happen?" You realise then that the PLO has been talking aboutjust such a possibility, that they have been staring into the darkness for the first time.
Last week's Arab-Israeli "summit of hope" in Cairo has not fooled the Palestinians. No date was set for long-postponed Palestinian elections on the West Bank, no date agreed for further Israeli "redeployment", no promises made of an end to Jewish settlement on Arab land. Mr Shaath's nimble mind has therefore been moving between the best and worst of all possible worlds, acknowledging failure and contemplating hope while excoriating those Palestinians who choose to oppose him.
"There are now three possible outcomes. The first is an alternative peace process in which we would go straight to the final settlement [talks on Jerusalem and Jewish settlements, the return of 1948 and 1967 Palestinian refugees], abandoning the interim settlement [elections and military withdrawals].
"So far, the interim process has failed. On both sides, it has failed," he says. "This interim stage was intended to improve the climate and build confidence between Palestinians and Israelis. But it is deepening the lack of confidence in the agreement
Sitting in his Cairo office Mr Shaath has rarely been so forthright. "The interim stage has not changed the image of Palestinians in Israeli eyes nor vice-versa. We were not able to give them more security. From their point of view, another Beit Lid [suicide bombing] will be the end of the road. From our point of view, more settlements are the end of the road. The idea of moving straight to permanent status discussions is gaining ground even in Israel."
The second option, Mr Shaath says, is "to live with closure, this wall of separation, for a while until something changes the balance of power, which means the Israelis will clamp down a new closure [on the West Bank and Gaza] until a new process has been found. We would have to build our relationships to Egypt and Jordan and build an economy that is self-sufficient for a while. We are working on this very fact."
And then he comes back to option three. "If number three ever takes place, it would eventually lead to a redefinition of the peace process. But it would meanwhile produce nothing for us and nothing for the Israelis. It would destroy both our goals of peace until it was replaced by something better. It would mean the collapse of the Palestinian authorities and resort to resistance again."
When asked how seriously he has contemplated this nightmare, he admits that he - though not Mr Arafat's "cabinet" - has contemplated a mass resignation of the Palestinian Authority, which would remain in Gaza but perhaps go underground. And he launches into a bitter attack on those Palestinians who, he believes, wish the peace process to fail.
"The intellectual opposition wants to make us look . . . incapable of meeting the Israelis at their own level of sophistication and connivance. Would they rather see a Bosnia or a Chechnya in Palestine? In the post-Soviet era, UN intervention has just stabilised the status quo in favour of the physically stronger party.
"Most of [the Islamic militants] Hamas's actions directed against the Israelis are in fact directed against us, to make us hit at them, to foment civil war or to make us look impotent to the Israelis."
Mr Shaath is now demanding the "Egyptian model" for peace. "Egypt took every Jewish settler and every settlement out and this produced a real peace. And in the West Bank, every settler and every settlement has got to go."
Jerusalem can be a capital for two nations, he says. "If the United States recognises all Jerusalem as the capital of Israel, that will end the peace process." He even talks about returning 1948 refugees to Galilee, inside Israel itself. "If you return 100,000 Palestinians to Galilee, that's only 10 per cent of the Palestinians in Israel already. Will the Israelis go along with that? I think they'll have to."
And then you realise that Mr Shaath wants what the Israelis thought they no longer had to contemplate: implementation of UN Security Council Resolution 242. Even if the nightmare third option was fulfilled, it would lead, after much blood, to another peace process because there is no going back.