The classic approach to corporate strategy starts with a presumption: that with sufficient analytical rigor and an adequate assessment of the probabilities, strategists can pave a predictable path to the future from the matter of the past. In this world, they make reasonable assumptions about the evolution of product markets, capital markets, technology, and government regulation and, in effect, "assume away" most risk. Chief executive officers articulate strategy every few years, often in the context of a change in top management.

Such traditional strategy formulation often pays lip service to the perspectives of the capital markets, to changing industry structures, and to the forces at work in the environment. But in reality, a "visionary" corporate strategy is often an internally driven reflection of what the company wants the world to look like.

But suppose we no longer believe that the future is foreseeable. What if defining and achieving an enduring competitive advantage is really just a conceit that must be abandoned? What if the outstanding fact of business, as John Maynard Keynes once described it, is the "extreme precariousness of the basis of knowledge"? What if it is no longer possible to block out the "noise" of the world's...