I viewed each patient as a dark room, and that, going into that room, in a session with the patient, I considered it essential to be slow and deliberate. Doing no harm, the most ancient of medical tenets, was on my mind all the time. There is more light to work with in externally visible illnesses; the Signs are more forcefully expressed, and therefore harder to miss. For the troubles of the mind, diagnosis is a trickier art, because even the strongest symptoms are sometimes not visible.
