The word habitually used by EU negotiators to characterise Boris Johnson's Brexit offer is "uncertainty". They talk of "uncertainty" about how the new customs border on the island of Ireland would work, about whether all the necessary checks could really take place away from the border. They say there is "uncertainty" about whether this new customs border would undermine the principle of sustaining an all-island economy.
They talk about "uncertainty" around the VAT regime for Northern Ireland and the EU. They talk about "uncertainty" about the operation of the single market for goods and food on the island of Ireland, and the proposed new checks on goods and food flowing back and forth between Northern Ireland and the Republic.
And of course they talk about the risk of permanent, corrosive "uncertainty" built into the new arrangements – in the unlikely event they were ever agreed – from Johnson's stipulation that the Northern Ireland Executive and Assembly would have the right every four years to close down the all-Ireland single market.
All of this means that there is zero chance right now of Johnson's offer being taken by EU negotiators into the so-called "tunnel" for the kind of detailed negotiation that could turn it into a ratifiable deal.
Because – in a nutshell – Johnson's offer is seen by negotiators not as rendering the backstop unnecessary, but as demonstrating precisely the opposite, that the kind of uncertainties implicit in what Johnson wants can only be eliminated with an insurance policy that kicks in unless and until Johnson's plan can be demonstrated to actually work.
And that insurance policy is called the backstop.
At the moment, Johnson is asking the EU to have faith in him that his plan will ultimately work, that all the uncertainties can be eliminated, while the UK remains a non-voting member of the EU, that is before the end of 2021 at the latest.
He is saying "trust me".
And the EU's response is "don't be ridiculous".
So the impasse is still there, more or less unchanged from what it was before Johnson even made his offer.
Maybe Johnson's chief negotiator, David Frost, has a rabbit in hat or pocket, to spring on Michel Barnier, his counterpart, this afternoon. But I doubt it. Partly because the big influence on Johnson, his chief aide, Dominic Cummings, has always said "read my lips, no rabbits, no compromise on the backstop".
Which means Johnson's offer is probably dead, there won't be a Brexit deal to put to MPs, and therefore all that matters now is whether MPs have or can yet obtain the power to delay Brexit and prevent a no-deal Brexit on 31 October.
Robert Peston is ITV’s Political Editor. This article originally appeared on his ITV news blog