One reason that political disagreements are often so enduring is that in the most heated cases there is rarely anything available which would count as proof, knocking dead one side of the debate and offering a definitive victory to the other.
For example, I have constantly pointed out in recent years that the settlements in east Jerusalem are a mere side issue in the broader conflict, that this is the only logical conclusion an objective observer could come to on the subject, and that, what's more, senior Palestinian officials have told me as much in private. But however many times I have said this, my opponents could simply reply that this was my own idea of what counted for objectivity and that my version of off-the-record briefings from unnamed Palestinian ministers counted for precisely nothing; I could have just made it all up.
No longer. Last weekend's leaks of secret negotiations between Israel and the Palestinians have emerged as game-changers in our understanding of how serious the Palestinians are (or rather are not) in the search for peace, while also proving what has long been alleged about the viciousness of many in Europe in their hostility to Israel.
Starting with the Palestinians themselves, two things are now unambiguously clear. The first is that when it comes to serious negotiations, they will adopt the same position that any rational person would adopt: the 1967 lines are largely irrelevant to a lasting agreement, therefore the vast majority of the so called settlements are a non-issue since they would simply become part of Israel anyway. The second thing we know is that they have been lying to their own people about the matter, as well as to the outside world. Intellectually and morally they have no problem with the settlements; politically and publicly they have not been preparing the Palestinian public for a resolution to the conflict. They thus lack all credibility as genuine partners for peace, as the Israelis have long known.
As far as the West is concerned, many of Israel's opponents have now been made to look, at best, like analytical dunces with no real understanding of the underlying dynamics, and at worst like hysterical ideologues taking a harder line against Israel on the settlements than the Palestinian leadership itself.
Monday's furious leader in the Guardian slating the Palestinian leadership as "weak" and "craven" for even intimating privately that the settlements were no big problem was possibly the most stomach-churning piece the paper has ever put out on the subject. They'd rather there was no peace at all than see the Palestinians make concessions that upset their ideological prejudices.
This has all been known for a long time of course. I could have written much the same a year ago. The difference is that today I've got the proof.
Robin Shepherd is Director, International Affairs at the Henry Jackson Society