The prime minister will make a powerful speech on Monday - in the heart of Brexit UK, Stoke-on-Trent - that MPs "all have a duty to implement the result of the referendum", because failure to do so would wreak "catastrophic harm" on "people's faith in the democratic process and their politicians".
Coming as it does from the most important and powerfully elected politician in the UK, this dramatic claim is worthy of careful consideration. What is it based upon?
Well it is founded on the premise, in her words, that "on the rare occasions when Parliament puts a question to the British people directly we have always understood that their response carries a profound significance".
That is an uncontroversial statement - though it is worth adding the rider that under the UK's unwritten constitution, referendums have "advisory" status, they do not mandate governments or Parliament in a binding way.
But May also points out that when her predecessor David Cameron wrote to voters just before the referendum campaigns began, he said "this is your decision; the government will implement what you decide".
It is on those foundations that she argues that a vote against her Brexit plan on Tuesday night would be a betrayal of the British people.
But is that the inescapable logical conclusion?
The PM marshals as further evidence that "as we have seen over the last few weeks, there are some in Westminster who would wish to delay or even stop Brexit and who will use every device available to them to do so".
That is where many MPs would see her as being mischievously disingenuous - because although there are MPs who hate Brexit in any shape or form, the Parliamentary action over the past few weeks has had a much narrower aim - namely to prevent a so-called no-deal Brexit.
The assorted forays by the likes of the senior Tories Sir Oliver Letwin and Dominic Grieve, and Labour's Yvette Cooper, have been shaped not to blow up all or any Brexit, but simply the version by which the UK would leave the EU in a possibly chaotic way and at alleged great economic cost on 29 March this year.
It is in May's conflation of her Brexit with any Brexit that she will anger and alienate both purist Brexiters and those who would rather the UK stays in the EU.
The important point is that there are many Brexiters who regard her own Brexit plan as betraying those who voted for Brexit.
And there are Remainers who argue that if the British people had known that Brexit would be her iteration they would never have voted for it.
Also, both sets of critics would point out something fundamental which is often overlooked - that in leaving on 29 March, we would be out of the EU without having much of a clue what kind of future trading relationship we would have with the EU, or how much commercial and lawmaking independence we would in practice enjoy.
All of that is yet to be negotiated.
To put it another way, on May's version of Brexit, what for many is the whole point of Brexit would be undecided for years to come.
That is why both Brexiters and Remainers would argue that a vote against May's deal would not remotely dishonour the referendum, since so much of what the referendum was all about is yet to be decided.
And they add that in voting for what they see as in the country's interest, they are honouring Britain's constitutional and democratic traditions, which could not - they would say - be the "catastrophic" blow to democracy that May avers it to be.
Quite the contrary, they would say - which is why I don't expect many of them to be swayed by May's speech.
Here is what one senior Tory said to me, after seeing the attack by May on MPs who have been employing Parliamentary devices to avoid a no-deal Brexit: "We are descending into banana republic status", adding that Tory rebels are "taking steps to protect the UK from a minority government gone mad".
As for the Brexiters, one of their number, who supports a no-deal Brexit, told me: "This is the most important vote in the Commons since the Norway debate [in 1940, which led to Churchill becoming prime minister] and the government and the EU are trying to stitch it up between them. It reeks to high heaven".
But if - as May's ministers tell me - there is therefore no possibility of May's speech seeing her home and dry in a couple of days, what follows? Is there anything else of importance to be read into what the PM is saying?
If her words are to be taken at face value, they imply a no-deal Brexit - however economically costly that may be - is what she would prefer over a referendum and no Brexit at all.
There must be a significant probability that a no-deal Brexit will become the Cabinet's official policy and not just the default option - albeit that several ministers would quit in protest.
Truthfully I am surprised to be writing this about the PM. I always thought that for May a no-deal Brexit was a bogeyman that would never be let out of the Downing Street cupboard. But her statement that it is her "duty" to implement the referendum result allows for no other conclusion.
Many in her own party openly disagree with her that a no-deal Brexit should be contemplated in any circumstances.
In words whose import were widely under-appreciated, Letwin - one of the more senior and respected backbenchers - said last week, when voting against what he called "my government" for only the second time in his life, he would continue to rebel against her as often as necessary, "right up to the end of March", to prevent no deal.
He and the former attorney general, Grieve, are seriously fed up with being accused by Downing Street of being traitors, when they feel that for years they have been more loyal to May than most of the Brexiters.
They and like-minded colleagues are examining Parliamentary procedure to see if on this they can seize the initiative and power from the prime minister, to empower backbenchers to veto no deal.
Meanwhile, Brexiters are engaged in a parallel process of seeing what can be done to prevent either government or MPs repealing or amending the existing legislation that would guarantee a no-deal Brexit in the absence of the approval of her deal.
This is momentous, titanic, the stuff of constitutional crisis, almost a new civil war.
But whether our democracy will emerge damaged or burnished is yet to be decided.