Uncertainty is a fact of life, but we have ever more to say about it. I always liked Peter Bernstein's way of summarizing progress in the field. At the same time, I never believed that because we have had a good conversation about it (slightly beyond "do not put all your eggs in one basket") that we knew enough to do any more than whistle in the graveyard. Nicholas Taleb famously makes this case. He elaborates in this recent econtalk podcast.
This is why I was perplexed by Kenneth Posner's Stalking the Black Swan. Posner owns up to his own recent investment missteps. He describes how he diligently applied all of the latest business school/Wall Street tools (Monte Carlo modeling, probability trees, correlation analysis), but came up short. His concluding chapter notes (what else?) that ya gotta have good judgment. What would Taleb say? It's not hard to imagine.