The paradox of this is that plans for tighter integration among the 17 euro zone countries are at the same time destined to create greater divisions within Europe — divisions between countries that use the euro and those that do not, and divisions within the euro zone itself, depending on the health and importance of the various economies. A two-, three-, four- and even five-tier Europe could possibly emerge.

“The markets have defined who are the good guys and who are the bad guys, and their interest rates are in many ways the manifestation of this,” said Alexander Stubb, Finland’s minister for European affairs. “When we look at future E.U. rules, it is the triple-A countries that are running the show.”

The political price of Britain’s self-proclaimed exceptionalism was made clear with a vengeance to Mr. Cameron on Wednesday, when he was pounded from all sides in a raucous session in the House of Commons. Fractious Europe-hating Conservative backbenchers called for him to stand firm on Europe, to “show bulldog spirit,” in a “resolute and uncompromising defense of British national interests,” as one legislator, Andrew Rosindell, put it.

Trying to placate them, the prime minister pledged not to sign anything that did not contain “British safeguards.”

Meanwhile, should the Europeans in the euro zone “go ahead with a separate treaty” that leaves out the noneuro countries, Mr. Cameron explained, “then clearly that is not a treaty that Britain would be signing or would be amending.” However, he said, he would still retain “some leverage” over the process.

“The more the euro zone countries ask for, the more we will ask for in return,” he said. But France and Germany have already made it abundantly clear that they will go ahead with their plans for the euro zone without regard to the needs or interests of Britain.