The biggest open question regarding the final deal is what enrichment capability Iran will retain. The Joint Plan specifies that there will be “a mutually defined enrichment programme with mutually agreed parameters consistent with practical-needs, with agreed limits on scope and level of enrichment activities, capacity, where it is carried out, and stocks of enriched uranium, for a period to be agreed upon.” Obviously this is rather vague, especially on the key point of whether Iran will be allowed to develop and deploy progressively more advanced centrifuges that would be a greater proliferation risk than the primitive models the country currently uses. But we should recognize that Iranian enrichment is a manageable threat. Smaller numbers of less advanced centrifuges simply take longer to make a bomb. Pairing limits with a strong inspection regime, like the one in the Additional Protocol, makes the threat even more manageable. The main work after a final deal would be ensuring that a strong coalition of nations remains committed to holding Iran to the terms. The worst-case scenario would be if Iran abrogated the deal and kicked out the inspectors, but only got a tepid response from the international community. For this to happen, there would have to be significant, likely preventable shifts in the dynamics of relations between the United States and other great powers, such that some of those powers would rather accept the danger of a nuclear Iran than cooperate with the United States to forestall it. (The Ukraine crisis risks moving things in that direction.) If we reach that point in our relations with other great powers, the problem of a nuclear Iran will be far less severe in comparison.

YET THE HAWKS IN WASHINGTON REMAIN BEDAZZLED by the prospect of confrontation. Their posturing in the wake of the Iraq War brings to mind Talleyrand’s comment about the Bourbons: “They had learned nothing and forgotten nothing.” And so, days before the interim deal was signed, a bipartisan group of fourteen senators issued a statement that they intended to pass new sanctions “as soon as possible,” saying that they were “committed to preventing Iran from acquiring [nuclear-weapons] capability.” The group, which included well-known hawks like John McCain, Lindsey Graham and Charles Schumer, enigmas like Tennessee’s Bob Corker, and Iraq War opponent Robert Menendez, promptly moved to make good on their word, proposing the Nuclear Weapon Free Iran Act a month later. If enacted, the measure would have tightened and expanded sanctions on Iran if it violated a range of strictures or failed to sign a final deal that met certain criteria.

The bill’s proponents sold it as a reasonable step to ensure Iran was negotiating in good faith. “Current sanctions brought Iran to the negotiating table and a credible threat of future sanctions will require Iran to cooperate and act in good faith at the negotiating table,” said Menendez in a statement. When the Obama administration pushed back, saying that the measure could scuttle the deal, National Review quipped that “if enforcing the terms of a weak existing bargain would imperil negotiations, that is as good a sign as any that, for now, negotiations are not worth holding at all.” And Senator Mark Kirk of Illinois, another key supporter of the bill, stated that it “would not impose any new sanctions during negotiations so long as Iran complies with the terms of the interim step agreement and concludes a final agreement to dismantle its illicit nuclear infrastructure.” Yet the bill did not merely serve to put teeth in the Joint Plan of Action. It was instead an alternative to it, drawing up parameters for a final agreement that did not match up with those that had been agreed upon in the Joint Plan. Had the bill been passed and had Iran then made a deal, even a generous one, under the Joint Plan, it would have still been hit with more extensive sanctions than ever before. The proposed legislation was thus a kind of de facto referendum on the Joint Plan—one that attracted fifty-nine cosponsors before an intense campaign against the sanctions by the White House and its allies in the press stalled it. Even AIPAC was backing away from the bill by the end.

Just where did the bill go wrong? It included a number of miscellaneous elements that added nothing to the legal impact of the bill, but which would have greatly influenced Iran’s interpretation of it, such as a declaration of the sense of Congress that “if the Government of Israel is compelled to take military action in legitimate self-defense against Iran’s nuclear weapon program,” the United States should support it with military force. It’s hard to say what this even means in practical terms—an Israeli military action against Iran’s nuclear-weapons program would be preventive and therefore not “legitimate self-defense” under the traditional laws of war; an Israeli military action in response to imminent or actual Iranian nuclear attack would be legitimate, but would almost certainly be supported by the United States, nonbinding resolution or not. A third reading, perhaps what some of the bill’s authors intended, is that it’s an attempt to stipulate that an Israeli preventive attack on Iran’s nuclear program would be “legitimate self-defense” (the word “legitimate” now being redefined to mean “supported by a statement from some legislative body somewhere”), and further that America should support it. Whether it’s prudent for Congress to declare our support before the fact for wars initiated at the leisure of a foreign government is a question we’ll leave for another day, but suffice it to say the Iranians would not take such declarations as signs of our good faith.

As Edward Levine of the Center for Arms Control and Non-Proliferation has pointed out, the proposed legislation would also link relief of the nuclear sanctions to two nonnuclear matters: the state of Iran’s ballistic-missile program and its support for terrorist activities. These are both critical areas of concern for U.S. national security, and that concern should be reflected in U.S. law. Yet that does not mean that they should be tied to the nuclear program (especially when resolving the nuclear issue would make Iran’s ballistic missiles and terrorist proxies a bit less threatening). It also does not mean that the best way for Washington to address its concerns about missiles and terrorism would be to breach the commitments it made in the Joint Plan of Action. Worse still, Levine notes that these linking clauses in the bill don’t specify a time frame, which could make them impossible to fulfill—to grant sanctions relief, the president might have to certify that Iran has never supported an act of terror against the United States (it’s done that before) or tested longer-ranged missiles (ditto).

But the worst feature of the Nuclear Weapon Free Iran Act is that it would move the goalposts set in the Joint Plan of Action. In the Joint Plan, the parties agreed that a final deal would “involve a mutually defined enrichment program with mutually agreed parameters,” and would “fully resolve concerns related to the reactor at Arak.” Yet under the bill, the final deal would have to “dismantle Iran’s illicit nuclear infrastructure, including enrichment and reprocessing capabilities and facilities, the heavy water reactor and production plant at Arak[emphasis added], and any nuclear weapon components and technology.” The bill and the Joint Plan are in direct contradiction on enrichment, and they’re in implicit contradiction on Arak. (And, as Levine observes, “How one dismantles technology is left to the imagination.”) The Iranians would complain if the legislation passed—and this time, they’d be in the right.

IN SUM, THE IRAN DEAL is not “surrender” or “Munich” or something even worse. It’s actually a positive, if limited, step. Indeed, it promises benefits that extend beyond what’s spelled out in the Joint Plan of Action. After more than three decades of enmity and mutual isolation broken only by secret, furtive contacts, the United States and Iran are now speaking regularly and openly. That’s important. Not communicating, even when relations are bad, is dangerous. It increases the chances of miscalculation and misunderstanding, and prevents potential areas of cooperation—which do exist—from balancing troubles in the relationship.

If the Joint Plan leads to a successful final deal that resolves the nuclear dispute, the unwritten benefits will be greater. Iran and the United States do not trust each other. Each has ample reason for that. That mistrust amplifies each side’s worries about the other—and makes behavior that will be seen as untrustworthy more likely. This unhealthy cycle has been on clear display with the nuclear issue: Iran builds secret nuclear facilities that make us think they’re up to no good; we mull attacking those facilities to head off evil intentions, which makes them more secretive, which makes us more worried, and so on. Cooperating to resolve a major strategic dispute gives each side an opportunity to test the other’s trustworthiness. The success of the Joint Plan could thus yield benefits in unexpected areas.

Of course, the Obama administration must remain clear-eyed in its view of Iran. At this point, calls in some quarters for a “grand bargain” or even an alliance savor of geopolitical naïveté. Iran’s government continues to be a major sponsor of terrorism. It is a rival to many of our allies, and though some of these alliances are not as close as they once were, they won’t be going away anytime soon. Iran talks like a revisionist power, and sometimes acts like one, too.