Artists and geniuses, and titans of commerce and global affairs, actively leave legacies. Beethoven reinvented the symphony, Picasso jolted us into abstraction. Gandhi taught us nonviolent resistance, and Bill Gates came up with the chip. Towering figures all. Legacies, immutable and eternal.

But we use "legacy" in a second sense, do we not? Chernobyl, for instance, has a legacy: UN-led efforts to reduce nuclear fallout. Here in the US, a notable example is that of the Triangle Shirtwaist Factory fire in Manhattan in 1911, in which 146 garment workers either died in the flames or jumped to their deaths, which helped propel certain reforms and the broader American trade union movement.

Tragedies don't actively leave legacies, but rather legacies are created out of their ashes. And this is the context – the only context – in which we must think about the legacy of blessedly exiting administration of George W Bush.

Am I being unfair? Is there not even one positive thing to say? OK. It was nice the other day, in fact quite nice, that Bush announced new protections for 195,280 square miles of American-controlled Pacific islands, reefs, surface waters and sea floor. That was well done. Bully.

But the world the Bushies tried to create – the legacy, that is, they attempted to leave has virtually nothing to recommend it. Even they know it. Vice-President Dick Cheney, in an exit interview with one of the last remaining friendly media outlets in the US (the Reverend Moon-owned Washington Times), said: "I'm personally persuaded that this president and this administration will look very good 20 or 30 years down the road in light of what we've been able to accomplish."

Now, let's parse why he said that. He knew he couldn't say with a straight face: "We've been incredibly successful and leave office with our heads held high." Even the man who said in May 2005 that the Iraqi insurgency was in its "last throes" couldn't pull that one off. At the same time, Cheney and other defenders can't say: "Well, we blew it, we screwed a lot of things up." The admission would be refreshing of course, but it isn't done.

So they are left with this stab in the dark. Bush's defenders surely know that even this scenario is bloody unlikely. But, you know, it could happen. So it's worth putting the spin on the record, just in case it does.

A list of grievances from the likes of me would be, I confess, a bit predictable and tedious, so there's no point in doing much besides briskly enumerating the lowlights, notorious and somewhat lesser known. The lies about the war. The phony Saddam–al-Qaida link. The use of one of our greatest national tragedy for partisan political purposes. The smearing of political opponents as unpatriotic. And in the face of all that, the temerity to botch of the prosecution of the war.

The corruption of the justice department. The torture, the waterboarding, Abu Ghraib. The domestic surveillance of only God yet knows who and what. Guantánamo. The intimidation of scientists, the doctoring of governmental reports on global warming. The utter inaction, also, on global warming. The utter inaction on healthcare. The utter inaction on the economy. The utter indifference – no, hostility – to any regulation of the mortgage market.

I promised I'd be brisk, but there's a little more. The phony "compromise" on stem-cell research. Katrina – ah, yes, New Orleans. Can't forget that. It, in turn, opens up an entirely fresh Pandora's box peopled with unqualified incompetents and unyielding ideologues who were given their government jobs merely, or at least chiefly, because they swore a mafioso-like fealty to capo Bush and consigliere Karl Rove.

One more and I'll stop. In 2003, the bookstore at the Grand Canyon mysteriously started carrying a book giving a "creation science" interpretation of the canyon, positing not that it is 4-5m years old, as rational people believe, but fewer than 6,000. After all, it couldn't be older than the Garden of Eden, right?

The wreckage – intellectual, ethical, moral, and physical, in terms of the lives lost by our soldiers and Lord knows how many Iraqis – is everywhere. The shame, even if Americans prefer not to admit it to Europeans, is immense. We know what we have done. We know how bad it is. If you watch US television news, you will see roughly half the people presented defending Bush. But that's only because TV has to strive for balance. Believe me, the real percentages are more like 80%:20%. Four out of five of my fellow citizens know we have erred.

For that reason, we can turn our attention now to Bush's legacies-from-the-ashes, positive and wholly unintended. Without his failures and, crucially, our collective acknowledgment of them, we would not have elected last autumn a man who is both a history maker and (seemingly) an intelligent and competent empiricist who believes in considering actual evidence (!) before making decisions. Without his failures and our collective acknowledgment of them, we would not be resolved as we are – some of us are merely resigned, but that's good enough – to start addressing our festering problems and proto-crises: our energy woes, our over-consumption of everything, our healthcare mess, our global condition.

The incoming president has a mandate to move on all these fronts. It is an astonishing and exhilarating thing to see; for the liberally inclined, an invigorating and, indeed, joyous time to be alive, as Wordsworth wrote à propos the French Revolution. Whether he will succeed, well, we shall see what we shall see. Without question, some hopes are too high. Human nature is human nature, despite what Marx and his inheritors thought. The communists couldn't change it, and Barack Obama won't change it either. He will succeed here and fail there.

But that isn't the question for today. We will have four or eight years to delve into all that. The question for today is, does the opportunity exist, at this historical moment, for a reordering of national and global priorities on a scale greater than anything seen since the Great Depression and the aftermath of the first world war? Yes, it does.

And for this, paradoxically, we have Bush to thank. Speaking of Marx, you know how the Marxists used to say "the worse, the better"? The dialectic hasn't always worked out they way they said it would, to put it mildly. But in the current case, it's playing out pretty perfectly, no? Bush made things so much worse, made it so evident to almost all of us, that things can only get better. Maybe in all that heavy reading he's allegedly been doing the last three years, Bush has a) become a secret liberal and b) dipped into enough Hegel to have learned how to set the dialectic in motion.

Or maybe he's just a really lousy president. Who was in over his head to begin with. I wonder how it feels, how it really feels, to know that, outside of the obvious mass murderers, you were one of the worst leaders in the history of modern world. Because he knows it. He'll never say it, but he knows it. I say, let him live with it, every day. And let the rest of us thank him for failing so colossally and then get on with the rebuilding.