The margin of defeat - 230 votes - leaves no doubt that something will need to change for both the EU and the UK to agree an orderly exit in the next few months.
But it would be a huge mistake to assume - as is so often assumed in Westminster - that it is now for the EU to reach into its negotiator's hat and pull out a rabbit that will save the British Brexit project.
Leader of the House of Commons Andrea Leadsom is one among many who believes this defeat sends a clear message to the EU that they must budge (presumably on the Irish backstop), but that is not where the thinking is on the EU side.
On the contrary.
When reports appear in British newspapers that Angela Merkel is about to offer "new concessions" on the backstop, blood boils in Brussels because the underlying presumption is that Brexit is a conundrum for the EU to solve.
As one exasperated EU official says, "It's the same old 'Germans to the rescue' storyline'."
The truth of that Monday conversation between May and Merkel was rather different. Indeed, it was almost the exact opposite, according to a Whitehall source with knowledge of the call.
The German leader focused on MPs needing to take responsibility and not just push everything back to the EU.
Because from an EU-perspective Brexit is not first and foremost a collective responsibility but a UK decision - or more accurately, a "non-decision decision".
For the last two years, the UK side has been politically incapable of reaching an internal agreement on what it wants.
It is from this that all of the current woes in this negotiation derive.
MPs who dislike the deal demand the EU must budge or give more concessions or that May should go back into bat. But, the EU asks, bat for what?
That is the question the EU wants answering. And after polite expressions of regret at yesterday's defeat, they can be expected to sit and wait to see what shakes out of the wreckage.
They will not want to be seen to be intransigent in Brussels. Indeed, Heiko Maas, the German Foreign Minister, said there was no reason there could not be further talks, but this offer should not be misconstrued.
It is true that EU officials, recognising reality, have started to talk about a willingness to extend Article 50 (at least until July) and even to reset negotiations entirely including (it is whispered) even reopening the Withdrawal Agreement if that is what it takes to get a deal.
But that "if" is all-important.
To make a new negotiation meaningful the UK side must turn up in Brussels with a cogent, negotiable position that convinces the 27 other EU leaders that it is worth reopening talks to get Brexit over the line.
Failure to do this - both in Salzburg last September, then again in December at the European Council - have ended disastrously for May.
In December, May demanded the EU guarantee her a trade deal by the end of 2021 to avoid the Irish backstop kicking in, but when asked how that would work, she was unable to answer.
She was, to quote Jean-Claude Juncker, "nebulous".
As a result EU leaders, already irritated at her decision to postpone the vote, shut up shop, slamming the door on any possible tweaks to the deal because they could not see how they would deliver Brexit.
Well now, in EU eyes at least, the time for nebulosity is over.
British MPs need to make decisions based on reality. No one (including British officials) wants to go back to the table to go through the motions of a negotiation to further indulge the delusions of some British politicians.
And as Maas intimated, the fundamental parameters of the discussion have not changed.
"The agreement stands as it is," he said.
"I doubt very much that the agreement can be fundamentally reopened. If there were a better solution it would already have been put forward."
Both the EU and the UK remain committed to avoiding a return to a hard border in Northern Ireland while forging a strong new trading relationship with the EU.
The border issue can be solved. MPs could go back to the "October" deal and accept a "de-dramatised" regulatory and customs border in the Irish Sea in order to repatriate full trade independence.
It could tack the other way and opt for a permanent customs union and high alignment with Europe, seriously cutting down hurdles that technology would need to solve, both north-south and east-west.
It could opt for an ultra-close single market and customs union deal, or even think again and decide that May's deal isn't so bad after all, since it leaves the door open to the very technological fixes championed by Brexiteers.
But, as EU officials say, the answers lie in Westminster, not in Brussels.
And if the UK can come up with half-decent answers they may yet be surprised at how much flexibility the EU will show to get the deal over the line when the final crunch comes.
We are a long way from there at the moment.
But the alternative is that, without a plan, EU leaders (just as they did at Salzburg and in December) may sit on their hands and simply refuse to extend Article 50 beyond a certain point.
That would present a stark choice indeed.
Since last year's European Court of Justice ruling, the UK has the power to unilaterally revoke Article 50, meaning the choice would be in British hands between a very hard landing, or revoking that letter and having no Brexit at all.
