Iran's rulers brutalize their own citizens, sponsor terrorism on several continents, and openly vow "death to America." They are determined to acquire the ability to develop nuclear weapons and deliver them to targets anywhere in the world.
Can President Obama stop them? That's not the question.
Or rather, that's not the question now being asked by the keenest observers of the diplomatic dance underway between Iran and the United States. What they are asking instead: Is Mr. Obama serious about trying to stop Tehran's revolutionary theocrats from becoming nuclear-armed, or is that not really his goal at this point?
"The fear," a former senior intelligence official told me, "is that the Iranians are going to pretend to give up their nuclear-weapons program - and we're going to pretend to believe them."
Similarly, Senate Foreign Relations Committee Chairman Robert Menendez, New Jersey Democrat, last week told a large audience at the annual Washington Forum of the Foundation for Defense of Democracies (the think tank I lead): "No one wants a diplomatic solution more than I do. But it cannot be a deal for a deal's sake. And I am worried [President Obama and his advisers] want a deal more than they want the right deal."
Michael Doran, a former senior director of the National Security Council, former Defense Department official, and now a senior fellow at the Brookings Institution's Saban Center, considered this possibility in a penetrating article in the journal Mosaic a few months back. He recalled that in 2012, Mr. Obama reiterated his pledge to do whatever might be necessary to prevent Iran from developing nukes - even if that necessitates the use of force. "As president of the United States," he emphasized to journalist Jeffrey Goldberg, "I don't bluff."
Subsequently, of course, Mr. Obama not only bluffed - he had his bluff called by Iran's client, Syrian dictator Bashar Assad. Mr. Obama had warned Mr. Assad not to use chemical weapons against his own people, and that if he did, he would cross a "red line" that would bring swift and painful punishment.
However, Mr. Doran wrote, after an August 2013 chemical attack that killed some 1,500 Syrians, "instead of ordering military action, the president decided to seek congressional authorization for the use of force, knowing full well that such a bill had little chance of passing."
Mr. Obama's aversion to the use of military power is understandable - and shared by most Americans. One of the clearest lessons of history, though, is that those who project strength end up using it sparingly, while those who project weakness invite their enemies to test them.