Henry Mintzberg did his Ph.D thesis studying 10 executives. He wrote a book about ten different role of a successful manager. Frederic Taylor invented the scientific management theory By observing the work in the factory!
Adam Smith studies the pin's factory and wrote a book about the Wealth of Nations...
What are the basis for good theory? Is it a statistical rigorous approach? Or is it à in depth understanding of the reality? How can we write a good theory which is a statement of causality! A Good theory help us to understand or predict the future