The skilled physician or farmer simply makes health or growth more certain and regular. We have all learned many things without the aid of a teacher. Some exceptional individuals have acquired wide learning and deep insight with very little formal schooling. But for most of us the process of learning is made more certain and less painful when we have a teacher's help. One basic aspect of teaching is not found in the other two cooperative arts that work with organic nature.
Teaching always involves a relation between the mind of one person and the mind of another.
The teacher is not merely a talking book, an animated phonograph record, broadcast to an unknown audience. He enters into a dialogue with his student. We might get by with encyclopaedias, phonograph records, and TV broadcasts if it were not for this intangible element, which is present in every good teacher-student relation. This is a two-way relation. The teacher gives, and the student receives aid and guidance.