Behind the histrionics of the US presidential race lies a profound fault line in Western political life. It is the division between those who think that only by talking can war be avoided, and those who think that sometimes only the threat of war can safeguard the right to talk and to live in freedom.

John McCain would use coercive pressure and military force if necessary to prevent the nuclear holocaust threatened by Iran or to pre-empt further attacks by Islamists. Barack Obama, by contrast, thinks war can be averted by talking to enemies to solve their grievances, and has said he would talk to Iran.

The notion that talking avoids war - a position otherwise known as appeasement - is a dangerous fallacy that has recently gained enormous traction in the West.

Both the Commons Foreign Affairs and International Development Select Committees have called for Britain and the West to start talking to Hamas. And at the end of October, the taxpayer-funded Institute of Contemporary Arts was due to host a debate between Usama Hamdan, of Hamas's governing council, and Alistair Crooke, a former British spy and founder of Conflicts Forum, which describes Palestinian terror as legitimate "resistance" and which has argued for "engagement" with Hamas. Paul M. Kennedy, a British historian at Yale, has written that for 70 years until the Second World War, appeasement was an established feature of British foreign policy. He defines it as a way of settling quarrels "by admitting and satisfying grievances through rational negotiation and compromise".

"Rational" is surely the key word. For appeasement breaks down when people pursue loathsome ends that are not amenable to negotiation or compromise, as with Nazi Germany or with Islamists who believe they are doing God's work in perpetrating genocide and conquest. History has shown us that far from preventing war, appeasement makes it more likely - and on terms favouring the aggressor. It was decades of appeasement, after all, that saddled us with our current crisis over Iran.

Straight after the 1979 Iranian revolution, the Carter Administration recognised the new Khomeini régime and offered to sell weapons to it. In response, the régime demanded the US hand over the Shah; and when it refused, Iran seized the US embassy and began 30 years of terrorism against the US and the West.

In 1997, Senator Joe Biden - Obama's running mate - encouraged trade and dialogue with Iran. The European Union followed suit by tripling its trade with Iran - which promptly diverted 70 per cent of the booty to its military and nuclear programmes. An Iranian spokesman explained: "We had one overt policy, which was one of negotiation and confidence building, and a covert policy, which was continuation of activities." Yes, it certainly pays to talk. The only question is: pays whom?

Sometimes, "back channel" talks to terrorists are unavoidable, as between Israel and Hamas in Gaza over the practicalities of life for the population. Intelligence agencies always need to talk to undesirables to get information.

But there's a huge difference between that and engaging terrorists in the public square, which gives them respectability, legitimises their "grievances" and validates their strategy of using violence to achieve political ends.

Such appeasement lies at the very heart of the eight-decade Arab-Israel conflict. When the Arabs used violence to thwart the 1920 League of Nations decision to re-establish a Jewish national home in Palestine, Britain responded not by enforcing its mandate to set up the home but by giving half of it to the Arabs.

The terrible lesson that violence pays has been repeated over and again in the Middle East. After the very first plane hijackings in the 1960s, the West responded by giving Palestinian terrorists a respectful hearing on the (spurious) grounds that their cause, if not their tactics, was legitimate. It treats Mahmoud Abbas's Fatah as a legitimate negotiating partner, despite its continuing involvement in terrorism, incitement to hatred of Israel and its declaration that it will never accept Israel as a Jewish state. Now people want to exacerbate that appeasement by talking to Hamas and Hizbollah. Obama has actually suggested that they have "legitimate claims". But what are they?

Their agenda - the destruction of Israel, the killing of every Jew - is both unconscionable and non-negotiable. "We are not fighting so that you will offer us something," said Hussein Mussawi, a former leader of Hizbollah. "We are fighting you to eliminate you." Talking to terror régimes empowers mass murderers and undermines moderates. So why is this disastrous proposal now running so strongly? One key factor is Northern Ireland, where the British establishment has convinced itself that it brought about peace by talking to the IRA. The IRA itself renounced violence because it had been beaten into a stalemate by the Army.

The deeper reason is the lethal coalescence of establishment fatalism, going back to the slaughter of the First World War and the subsequent collapse of Britain's sense of national purpose, with the agenda of the "transnational progressive" Left, whose refusal to countenance war in the defence of national self-interest is part of its programme to destroy Western nations altogether.

The history of the 1930s is thus repeating itself, once again as tragedy.