A principal argument opponents raise against the nuclear agreement with Iran is that it would release at least $100 billion in impounded funds that Tehran could then use for attacks against the West and others. But exactly how much money the Iranians would actually receive and how they would use it, should the accord survive, remain difficult and unresolved questions.

The best answer appears to be that nobody really knows, not even the Iranians themselves. As in the broader dispute over whether the agreement would block or pave Iran’s pathways to a nuclear weapon, conflicting claims on both sides have clouded the issue.

The money sits in foreign banks, out of Iran’s reach. Estimates of the sum that could become available to Iran range from $29 billion to as much as $150 billion.

Accumulated partly from Iranian sales of oil and other goods, the money is one of the most important, and perhaps misunderstood, components of the nuclear deal reached last month.