There is nothing like a crisis to clarify the mind. In suddenly volatile and different times, you must have a strategy. I don’t mean most of the things people call strategy—mission statements, audacious goals, three- to five-year budget plans. I mean a real strategy.

For many managers, the word has become a verbal tic. Business lingo has transformed marketing into marketing strategy, data processing into IT strategy, acquisitions into growth strategy. Cut prices and you have a low-price strategy. Equating strategy with success, audacity, or ambition creates still more confusion. A lot of people label anything that bears the CEO’s signature as strategic—a definition based on the decider’s pay grade, not the decision.

By strategy, I mean a cohesive response to a challenge. A real strategy is neither a document nor a forecast but rather an overall approach based on a diagnosis of a challenge. The most important element of a strategy is a coherent viewpoint about the forces at work, not a plan.

What’s happening?

The past year’s events have been surprising but not novel. Historically, land bubbles, easy credit, and high leverage often make a dangerous mixture. Real-estate debt triggered the first US depression, in 1819. A land...