The central question about Iran, as Henry Kissinger has observed, is whether it wants to be a nation or a cause. In the case of President Mahmoud Ahmadinejad, it s clearly a revolutionary cause. He has said as much himself in an intriguing and occasionally bizarre series of public letters to America.

The revolutionary zealotry of Ahmadinejad is among the obstacles the Obama administration faces as it prepares for Oct. 1 talks with the Islamic republic. As Ahmadinejad s letters make clear, he doesn t want a seat at the negotiating table with the great powers; he wants to overturn that table.

Ahmadinejad defies not only the United States, but the entire system of international relations that was created in 1945. He sees the world "at the threshold of entering a new era." He wants a "reorganization" of the United Nations, the Security Council, global media networks and other institutions. "The existing mechanisms are not capable to meet the present needs of mankind," said Iran s message this month.

There s an echo of Robespierre or Mao Zedong in his talk of a new order that enfranchises the dispossessed. "I congratulate you," he wrote to Obama a day after the presidential election, warning in the same breath that "the nations of the world expect an end to policies based on warmongering, invasion, bullying, trickery [and] the humiliation of other countries."

Ahmadinejad s most peculiar epistle was his May 8, 2006, letter to President George W. Bush. "For some time now I have been thinking, how one can justify the undeniable contradictions that exist in the international arena," he began. Noting that he was once a teacher, he prodded Bush like a nettlesome inquisitor, asking how he could call himself "a follower of Jesus Christ" and yet pursue aggressive policies.

The Iranian president is even a "truther," insisting that there was a hidden hand behind Sept. 11, 2001. "Could it be planned and executed without coordination with intelligence and security services—or their extensive infiltration?" he mused in the letter to Bush.

Ahmadinejad always expresses his scorn for Israel. A Nov. 29 letter to the American people contained this bit of blatant anti-Semitism: "What have the Zionists done for the American people that the U. S. administration considers itself obliged to blindly support these infamous aggressors? Is it not because they have imposed themselves on a substantial portion of the banking, financial, cultural and media sectors?"

Ahmadinejad, thankfully, is not the only political voice in Tehran. Other political figures there make clear in private contacts that they see Iran as a nation—with pragmatic interests that can be served by negotiation. Obama s challenge is how to connect with them. Through engagement, he should push Supreme Leader Ali Khamenei to make a choice: Can Iran shed its revolutionary rhetoric enough to speak the language of national interest?

We should credit the Obama team for its deft approach to engagement. U. S. officials invite negotiations but, like good merchants, they never name their price. They extend the hand of friendship, thereby depriving the Iranians of their favorite villain. They suggest a time limit for talks but are fuzzy about when it ends. Perhaps most important, Obama is subtly turning up the pressure on Tehran, even as he invites dialogue.

That s the importance of the announcement that the United States is shelving its plans for missile defense sites in Poland and the Czech Republic. Officials may deny there s any quid pro quo—any reciprocal promise of Soviet support for sanctions against Iran if negotiations fail. But the Iranians will worry, just the same.

That s hardball negotiating: Make them sweat in Tehran. Make them worry that unless they start acting like a nation, they will face growing isolation, economic pressure and internal unrest.

The Ahmadinejad papers are a reminder that a pragmatic bargain with this man is probably impossible. He s a revolutionary, not a dealmaker.