From the standpoint of producing Middle East peace, President Donald Trump's decision to recognise Jerusalem as the capital of Israel can only be called irrational.
It raises the risk of Palestinian violence that could derail peace efforts by his son-in-law, Mr Jared Kushner. It makes it harder for crucial US allies like the Saudis to side with Mr Trump and push the Palestinians to a deal. It won't make Israel feel more secure. And it will hearten right-wingers in the US and Israel whose endgame is actually to avoid a two-state solution.
Yet there is one possible silver lining to the coming storm - a consequence of the decision that may affect the calculus of the peace process more positively.
Mr Trump, intentionally or not, is signalling to all concerned that he is unafraid of backing Israel in ways that go further than the traditional pro-Israel US stance. That's a huge threat to the Palestinians - if peace talks fail, Mr Trump could be prepared to support Israeli annexation of more of the West Bank. And it's an implicit promise to the Israelis that also contains an implicit threat: Given how generous Mr Trump is being to Israel, its leaders had better agree to whatever deal Mr Trump will seek to impose on them - or else.
To see why Mr Trump's move is so extraordinary, you have to understand that the recognition of Jerusalem as Israel's capital amounts to a recognition of Israel's unilateral annexation of East Jerusalem - and its subsequent expansion of the Jerusalem municipality far beyond the cities' traditional limits to include multiple Palestinian villages and newly built Jewish neighbourhoods.
If recognising Jerusalem as the capital only meant acknowledging that the Knesset and the rest of Israel's governing institutions are there, it wouldn't be quite so big a deal. They've been in the western part of the city since Israel's independence in 1948. Countries presumably have the right to choose any city they want as their capital. And no one realistically thinks that West Jerusalem shouldn't be part of Israel under a final status agreement. The tricky part is that, since 1967, Israel has considered East and West Jerusalem to be a single, unified city, at least as a legal matter. (Lots of differences exist on the ground.)
The act of annexing Jordanian territory into Israel has not been recognised by the international community, including the US. Israel has deepened the problem by successive further expansions of Jerusalem that themselves have come with further annexation. Today, the Jerusalem border extends almost all the way to Bethlehem, south of the city. Although recognising Jerusalem as Israel's capital doesn't necessarily entail formal recognition of Israeli annexation of East Jerusalem, it certainly suggests that the Trump administration is willing to come very close - far closer than any prior US administration. That carries meaning for the Palestinian and Israeli negotiators alike.
It hints that Mr Trump is willing to threaten the Palestinians with endorsement of Israeli annexation of more Palestinian territory - a nightmare from the Palestinian perspective. The fact that Mr Trump is so blatantly pro-Israel suggests that the Palestinians had better bend over backwards to accept whatever deal is on offer, lest the consequences be dire.
Once Mr Trump has shown such solicitude for Israel, giving it the recognition it has long claimed it wanted, he will want a lot in return.
To be exact, the Trump administration is going to insist that the Israelis not spoil the Kushner peace plan, which (if it succeeds) is sure to be rebranded as Mr Trump's. Prime Minister Benjamin Netanyahu can reliably be counted on to say that his coalition won't let him take any deal at all. Mr Kushner and his team know that, of course. The basis for the secret threat to Mr Netanyahu will have to be that, as the most nakedly pro-Israel president ever, Mr Trump has the clout to blame Mr Netanyahu if he is truly responsible for the breakdown of the deal. Mr Trump can say what no other president could: That the world, including pro-Israel American Jews, will believe him if he says Mr Netanyahu is the problem and that he should no longer be prime minister. Mr Trump could even credibly threaten that US support for Israel would be substantially reduced in the future if Mr Netanyahu blinks.
Remember: America first - which means Trump first - is perhaps the only principle that can trump Trump's pro-Israel approach. The Israelis have got the recognition they wanted. Now they will have to pay for it, one way or another.