US Secretary of State John Kerry has accurately described the current thaw in US-Iranian relations as an “opportunity,” frustrating Kerry's critics who see the recent Iranian efforts as simply a charm offensive aimed at fooling the West, and exasperating the chorus of Iranians who retain an almost genetic opposition to anything American.

Even those who oppose engagement as a trap aimed at enabling an Iranian pursuit of nuclear weapons acknowledge Kerry's assessment, while belittling its importance. “Show us the money,” goes the cry, demanding irrefutable evidence that it is not just the music that has changed, but also the lyrics.

Kerry himself has adopted this practical and entirely understandable standard. “President [Barack] Obama has said, and I think other the members of the P5+1 agree,” said Kerry at his Oct. 6 meeting in Bali with Russian Foreign Minister Sergey Lavrov, “it's not words that will make the difference.” Iran, too, can surely be counted among those who also expect practical, operational results — and sooner rather than later.

Words may not make the difference, but they make a difference. It matters that Ayatollah Ali Khamenei has called for “heroic flexibility.” Kerry has in fact led this effort on the American side. He pronounced himself “encouraged by the [Iranian] statements that were made in New York, and we're encouraged by the outreach.”