I once had a professor who was fond of saying that "we know much more than we understand." At the time, I really did not appreciate what he meant. But over the years I have had a number of experiences that have made the distinction clear to me. For example, I once worked with a child psychiatrist who did magnificent work with children. He got results when no one else could and literally performed miracles, but he could not articulate his clinical skills. When he spoke to students and colleagues, he seemed unable to conceptualize the clinical insights that guided his therapy. Rather, he described his work in terms of traditional therapeutic concepts that seemed rather far removed from his actual clinical practice.
Another example may help to make this distinction between knowing and understanding a bit more concrete. I once visited a lovely nursery school in Los Angeles. It