ANYONE who has tried a hand at starting a high-tech business—seeking to turn a clever research idea into something customers will pay good money for—quickly learns that everything taught in business school is next to useless. The mistake is to think of start-ups as just smaller versions of established businesses. They are nothing of the sort.

Difference Engine: Pilgrim's progress

ANYONE who has tried a hand at starting a high-tech business—seeking to turn a clever research idea into something customers will pay good money for—quickly learns that everything taught in business school