Mixing shrewd diplomacy with defiance of U.N. resolutions, Iran has turned the negotiation on its head.

The announced framework for an agreement on Iran’s nuclear program has the potential to generate a seminal national debate. Advocates exult over the nuclear constraints it would impose on Iran. Critics question the verifiability of these constraints and their longer-term impact on regional and world stability. The historic significance of the agreement and indeed its sustainability depend on whether these emotions, valid by themselves, can be reconciled.

Debate regarding technical details of the deal has thus far inhibited the soul-searching necessary regarding its deeper implications. For 20 years, three presidents of both major parties proclaimed that an Iranian nuclear weapon was contrary to American and global interests—and that they were prepared to use force to prevent it. Yet negotiations that began 12 years ago as an international effort to prevent an Iranian capability to develop a nuclear arsenal are ending with an agreement that concedes this very capability, albeit short of its full capacity in the first 10 years.