It’s quiet – too quiet.” It was, I think, John Wayne who first drawled that line of knowing scepticism, in the 1934 B-movie western The Lucky Texan. But it seems no less apt this week, as the Tory prairie remains suspiciously peaceful in response to Theresa May’s speech on Brexit, delivered at the Mansion House on Friday. True, Michael Heseltine has performed his quasi-constitutional role as lord privy Europhile by dismissing the prime minister’s remarks as no more than “phrases, generalisations and platitudes”. There are reports too of a dirty tricks operation at No 10 to undermine the foreign secretary, Boris Johnson, (vigorously denied all round).

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Yet the Conservative reaction to the speech has been remarkably cordial. Less than a week ago, it was bellicose business as usual. On the eve of the prime minister’s big speech, John Major declared that “many electors know they were misled” over Brexit, that “many more are beginning to realise it”, and: “The electorate has every right to reconsider their decision.”

The reality TV star and occasional MP Nadine Dorries branded Major a traitor for his outrageous suggestion that the public might be consulted again on Britain’s EU departure. And quite right too: this is obviously no time for careful reflection, caution or hard-won wisdom – the telltale sneaky weapons of “saboteurs”, “enemies of the people” and other foes of the popular will.

Yet the gunfire that preceded May’s speech has, for now, fallen almost entirely silent. On the blasted mud of no man’s land, you can see Jacob Rees-Mogg kicking the ball amiably to Anna Soubry, who heads it back to Iain Duncan Smith. Where there was discord, there is, as St Francis of Assisi might observe, a sudden and unexpected harmony. Or so it seems.

The second driver of the present Tory truce is undoubtedly Jeremy Corbyn’s shift of position

Why so? First because, of all May’s significant strategic interventions on Brexit to date, this was the crunchiest and most substantial: plunging into the weeds of policy, recognising some of the “hard facts” of what lies ahead, and acknowledging that “no one will get everything they want”. Much of what has been obvious but unstated was at last made explicit.

There was also something for everyone, which is another way of saying that detail is not the same as decisiveness. For the Brexiteers, there was the repeated guarantee that Britain will leave the single market and customs union; that, in due course, parliament can diverge from EU standards as much as it sees fit; and that May herself will not countenance “anything that would damage the integrity” of the UK. On the BBC’s Andrew Marr Show today, she was emphatic that “we would just be a rule-taker” if “financial passporting” – the special arrangements that allow banks and other City companies to operate across the EU – were left in place.

For remainers, on the other hand, there was the reassurance that Britain will continue to be associated with a host of EU agencies; that May will adopt a practical approach to the future role of the European court of justice; and that, on workers’ rights and other social protections, “We will not engage in a race to the bottom.”

The second driver of the present Tory truce – though few Conservatives will admit it – is undoubtedly Jeremy Corbyn’s shift of position last week on Britain’s future relationship with the EU customs union. The Labour leader’s subordination, after much deliberation, of his career-long Eurosceptic instincts to an overtly political strategy has brought home to those Conservative MPs who are paying attention that Corbyn is not just the man who might be propelled into No 10 by Tory incompetence. He really wants the job, and he intends to get it. The Tories are spooked, as well they might be.

As an exercise in tactical party management, therefore, May’s speech was a success. But that’s all it was. The Conservative dilemma over Europe is structural rather than specific. It has bedevilled the party for 30 years, destroying its last three prime ministers, and it may yet claim a fourth before too long.

Here’s the irony: David Cameron’s referendum gamble was meant to solve the problem once and for all, but it has had the bleak effect of compounding it. The wisdom of his decision remains a matter of fierce debate at Tory tables. But he is not to blame for the deeper tribal pathology, which has been reinforced rather than resolved.

One half of the Conservative psyche, well described in an essay by William Davies in the current London Review of Books, is positively drawn to the stoic challenge of Brexit, believing that “toughness, even pain, performs an important moral and psychological function in pushing people to come up with solutions”.

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In fundamental tension with this is an alliance of older Tories, who believe in the postwar dream of European harmony, and of pragmatic Conservatives who consider exit from the world’s largest single market and one of its most powerful alliances to be an act of collective self-harm.

I think they are right. But that is not the point. The gulf between the two positions – stoic independence versus practical internationalism – is ultimately unbridgeable. One must prevail, and the moment of victory and defeat has been deferred, not confronted. There is much political blood left to be shed, as each chapter of the negotiations unfolds.

“Now is not the time to nitpick,” wrote Rees-Mogg in Saturday’s Telegraph. But – by heavy implication – that time will come again. The prime minister’s speech was a mere sticking plaster on an old and suppurating wound. Enjoy the peace while it lasts, for it will not last long.

• Matthew d’Ancona is a Guardian columnist