N. A. Freeman tells a story about when she was a student nurse. She was assigned to the care of a young man stricken with a paralyzing disease. He had lost his ability to speak, although his understanding and intelligence were unimpaired. Ms. Freeman was determined to keep him cheerful. Day in and day out she talked to him of the weather, baseball scores, the latest movies, her classmate who eloped, and whatever else she could think of.

Months later, Ms. Freeman received a summons to his doctor's office, "to see what progress her ex-patient had made." His speech therapist explained that she had been invited to hear the first words that her patient had spoken in three years, the words that he had asked to be taught first. As she walked in, she was greeted by a big smile on the young man's …