With the ink barely dry on the interim nuclear deal signed Sunday between Iran and six world powers in Geneva, there's already a battle to define it. President Obama called the six-month pact “an important first step toward a comprehensive solution.” Israeli Prime Minister Benjamin Netanyahu—echoed by some congressional Republicans—called it a “historic mistake” in his weekly cabinet meeting.

Who is right? The answer depends on what one is comparing the deal to.

Compared to the ideal no-enrichment deal sought by Israel and the Gulf states—nay, compared to Iran’s obligations under U.N. Security Council resolutions—Geneva was indeed a lousy deal. The six-month agreement does not oblige Iran to suspend all domestic uranium enrichment, offering de-facto recognition of the dubious right that Iran has been claiming under international law. Iran will also get economic relief to the tune of $6-7 billion in unfrozen assets and relaxation of sanctions on precious metals, refined-oil products, and automobile and aircraft parts. As many have pointed out, the improvement to the Iranian economy is likely to be far greater, as the expectation of future sanctions relief changes the psychology of outside investors.

But a more useful way to evaluate the Geneva deal is to compare it to a scenario in which the talks produced nothing. From this perspective, the deal is a clear victory, even for Israel.

Before Geneva, Iran was steadily increasing its number of centrifuges and installing new, advanced ones. The steady increase over recent years had shortened the breakout period—that is, the time it would take Iran to produce enough weapons-grade uranium for a bomb—to as little as six weeks. By barring the introduction of new centrifuges and placing limits on the existing ones, the deal will lengthen the breakout period by 1-2 months.