… Drucker went on to tell us that it was essential that business executives master at least two disciplines, and that one of them must be outside of the field of business. He said this was important in the preparation of an executive for higher responsibilities because, like the corporate attorney suddenly elevated to general management, one never knew what future responsibiliteis might be thrust upon one unexpectedly. Expertise in more than one field was good training for sudden responsibilities in yet another field, and was the only evidence that the manager was capable of mastering more than one discipline.
Peter said that mastering at least two disciplines would have a number of beneficial effects. First, the executive would have the self-confidence of knowing that he was not limited to a single field. That he could, if called upon, do something entirely different, and do it well. Moreover, Drucker continued, great advances in any field rarely come from a single discipline. Rather they come from advances in one discipline being transplanted to another sphere, which is totally unfamiliar with these procedures, ideas, or methods which have never been applied to problems in this other domain” (p 74).
This is worth repeating: great advances in any field rarely come from a single discipline; rather they come from advances in one discipline being transplanted to another sphere.