The centennial memoir of his famous parent by Ron Reagan ( My Father at 100), which at first sight looks as slight as its author, is better than many press reports might suggest. For example, the younger son by no means “cashes in” on the idea that our 40th president was suffering from Alzheimer’s well before he left office; he simply adds his own private observations to what has since become perfectly obvious. A number of things apart from cognitive decay could have curtailed Reagan’s two-term reign. He might easily have died after being shot in March 1981, and indeed he was much closer to death than anybody realized at the time. He should certainly have been impeached and removed from office over the Iran-Contra racket, in which he was exposed as the president of a secret and illegal government, financed with an anti-constitutional hostage-trading and arms-dealing budget, as well as of the ostensibly legitimate one. The question that keeps recurring to me is this: Would the country and the world have been better off without his tenure of the Oval Office?

I lived in Washington for most of those eight years, and for most of them would have replied with an unhesitating “yes.” (To this day I refuse to call my local airport “Reagan,” since before the name change it was Washington National, which means, thanks very much, that it was already named for a perfectly good ex-president.) Even now I can easily remember the things that outraged me: his easy manner when lying and his sometimes breathtakingly reactionary views. These extended from the whitewashing of the SS graves at Bitburg to his opinion that Americans fighting for the Spanish Republic had been on the “wrong” side, to his discovery that apartheid South Africa had always been an ally of the United States. Then there was the abject scuttle from Lebanon and the underhanded way in which Reagan tried to blame it on the Democrats. Perhaps worst of all was an apparent fusion of two things: his indulgence of fundamentalist and millennial priestly crooks like Jerry Falwell and his seeming flippancy about nuclear war. He once maintained that intercontinental missiles could be recalled after being launched, made on-air jokes about blasting the Soviet Union, and fatuously intoned “May the Force be with you” after announcing his plan for a Strategic Defense Initiative, or “Star Wars.” The coincidence between his superstitious interest in “End Times” theology and his insouciance about nuclear matters seemed dire in the extreme. And then there was Alexander Haig as secretary of state, and Oliver North as confidant, and the wife with the astrologer …

In a bizarre way, though, his simple-mindedness turns out to have had a touch of genius to it. His grasp of physics was on a level with Hollywood beam-weapon B-movies, and how we all laughed when he told Mikhail Gorbachev that, in the event of a Martian invasion of Earth, the United States and the Soviet Union would combine to sink their differences. But he had an insight that was denied to the adherents of Mutual Assured Destruction, whose theory was rapidly coming up against diminishing returns.

Young Reagan rightly draws attention to a forgotten moment at the forgotten Republican Convention of 1976. Having only narrowly defeated him, Gerald Ford felt obliged to call on Reagan to join him on stage after accepting the nomination. Reagan took his sweet time to come to the podium, where he was already the darling of many delegates. And having done so, he said not a word in praise of Ford or his running mate, Bob Dole. Instead, he spoke about being invited to contribute something to a “time capsule” that was being readied in Los Angeles and was scheduled to be opened 100 years later. Those who opened that capsule, said Reagan, would know whether or not Armageddon had been avoided. “We live in a world in which the great powers have poised and aimed at each other horrible missiles of destruction, nuclear weapons, that can in a matter of minutes arrive at each other’s country and destroy, virtually, the civilized world we live in.”

Of course there’s an anachronistic contradiction there, in that had the weapons been used, the time capsule would never have been opened, but why quibble? It was an unusual way for the losing candidate of the right to address the faithful. A bit more than 10 years later, I was having a drink with Timothy Garton Ash in the Glasnost Café, as the coffee shop of the Marriott Hotel in Washington had been renamed while it hosted the joint press conferences of the Reagan and Gorbachev summit. * Outside, right-wing Republican nuts wearing Reagan masks were angrily flourishing umbrellas, in order to compare him to Neville Chamberlain in Munich. I said: “Well, we’ve lived to see it. The end of the goddam Cold War.” Within a much shorter time, the Berlin Wall had gone, and I could verify from the people who had written Reagan’s celebrated “tear down this wall” speech that he had insisted on the insertion of these words over the objections of many “realists.”

It was extraordinary that, in Mikhail Gorbachev, Reagan was dealing with a man who knew that the Soviet Union could not sustain the arms race and a man who was out of patience with the satraps of East Germany. To Gorbachev goes an enormous share of the credit. But if I run the thought experiment and ask myself whether Walter Mondale would have made a better interlocutor in 1987, I cannot make myself believe it. This does not involve un-saying any of the things about Reagan that his admirers would prefer us to forget. But it does acknowledge the distinction between a historic presidency and an average one. Reagan’s friend Margaret Thatcher once said that the real test of her success was the way that she had changed the politics of the Labour Party. By that standard, the legacy of Reagan in permanently altering the political landscape is with us still.

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Correction, Feb. 5, 2011: This article originally placed the conversation with Timothy Garton Ash at 20 years after the 1976 Republican Convention. (Return to the corrected sentence.)