For some reason, it is easier to recognize 2010 as the last year of the new millennium's first decade than it was ten years ago to recognize Y2K as the final year of the twentieth century. 2000 felt like something new. That New Year's Eve ten years ago, people around the world indeed partied "like it was 1999," feeling that the entrance of that numeral "2" was the start of something big. I suspect that the celebrations this year will be much more subdued, because, let's face it folks, we got off on the wrong foot.

Not that the last one hundred years were so wonderful, featuring world wars, global genocides, and a nuclear arms race threatening Armageddon. Still, the achievements of the 80s and 90s, featuring the collapse of the cold war, progress on human rights, and extraordinary developments in a full spectrum of life-enhancing technologies, imbued us with a visceral sense of optimism as we crossed the bridge to a new century. Our confidence was reinforced when the world did not end the morning of January 1, 2000, and traffic lights and air traffic controllers continued to function despite their ancient software. We were even smarter than we thought.

But as we threw away our duck tape, the dot com bubble burst, along with the Twin Towers and the world as we knew it. And what followed were more wars and bursting bubbles, a rough ride downhill almost to another great depression. New York Times columnist Paul Krugman wants to call the decade "the Zeros" because nothing good happened, but we know all too well that there is something worse than nothing good. Indeed, the disturbing theme of this first decade of a new time in human affairs has not been the absence of something good, but rather the hidden presence of something very bad, like biting into a shiny, hard apple and finding nasty rot inside.

We saw this motif again and again. That great stock you bought was actually worthless. The average looking guy sitting next to you on the airplane turned out to be a terrorist. The company that posted record profits was actually sinking like the Titanic. The miraculous energy company was actually an energy black hole. The war against terrorism was actually a terrorism factory. The quest for imaginary weapons of mass destruction somehow managed to produce mass destruction itself. Moral crusaders (there were many) turned out to be immoral philanderers in disguise. The insurance company turned out to be a casino. The guardians were thieves, the buttresses were battering rams, and the rock turned out to be quicksand. Donning their bleeding red brackets, assets revealed themselves as liabilities. The world seemed (indeed, seems) to be rife with "Black Swans." The impossible was not merely possible; it was real and it arrived in the flesh. As a person who grew up in the shadows of Manhattan, what I still cannot process when I look at the New York City skyline is the absence. The empty space visibly towers, serving as a stark reminder that what seems permanent and trustworthy can change in a moment.

The word I will associate with the transition to a new decade this year is "risk." It's a good word to contemplate in a blog dedicated to the practice of courageous leadership. I really hate to quote Donald Rumsfeld, but back in 2002, he said it right:There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.

Real risk is not just about the known unknowns, it is about the unknown unknowns. The Zeros have been a decade dedicated to these special risks: that treacherous floor beneath your feet that looks and feels secure but is about to give way. How do you marshal courage against the unknown? It's a very hard case, because a mature, pragmatic courage calls upon us to carefully weigh the costs and benefits of a particular choice. But when we are actually in the arena, rather than on the sidelines pontificating, we not only lack information, we often labor under lies and deceit, and so the risks we confront are often painfully hidden and unknowable to us in the difficult moment when we must make our way forward.

While humans as a whole are gaining increasing mastery over the world they inhabit, they remain sharply vulnerable to one another and to their own systems. This is the special teaching of the first decade of the new millennium. The greatest global threat to the natural lifespan is no longer nature but humanity, menacing not only itself but every other life form on earth as well. At this moment in human evolution, courage acquires a special meaning. Courage no longer dwells in confronting the risks "out there," nor even the risks posed by "others." The special courage called for in the third millennium is the grit needed to stare deeply into the mirror and to know ourselves. That which lies hidden within human nature itself is surely both our greatest asset and our most profound liability. The courage we must call forth now is the capacity for self knowledge and self control.