In a Feb. 25, 2009 Financial Times piece Insight: The flight of the long run by Peter Bernstein , he comments that "The unknown today seems more than usually unknown. Then my whole point remains the same. The long run is an impenetrable mystery. It always has been."
He also cites John Maynard Keynes' observation about the future: "We simply do not know."
Amen to those ideas!