When someone is studying to become a doctor, he can learn a lot from professors and textbooks. But there are some things he will have to actually experience, in order to learn them.
Like diagnosing a patient, for instance. Figuring out what’s wrong with someone when he comes into the emergency room complaining of a “sore stomach” or a “severe headache.” Those two symptoms could have many different causes—anything from a gas bubble to appendicitis.