I'm an optimist by nature. It's one of my failings as a journalist, I suspect. But I find it hard to be as optimistic about the course of the global economy as Swaminathan Aiyar. Yes, strong global demand is helping push up oil prices, and yes, a mild recession would help curb the U.S. consumption binge that produces such big trade deficits. And maybe we'll have yet another "soft landing."

But if there's one thing the last decade should have reminded us, it's that the economic law of gravity has not been suspended. What goes up does come down. What's unsustainable is not sustained. Big imbalances do have consequences. Markets do correct--and in doing so, they often overshoot.

The Fed and European central banks have been pumping new billions of liquidity into the international financial system (largely unnoticed) for a reason: They are nervous. So am I. A wise central banker commented to me recently that the best policy advice in such a delicate situation is the Hippocratic Oath: Do no harm. In other words, don't do anything rash to react to the repricing of assets and currencies that's now taking place. I hope that advice is followed. I hope it works. As I said, I want to be an optimist....