This paper presents two propositions: (1) that extensive knowledge of subject matter is a necessary but not sufficient condition for effective teaching; and (2) that teacher education is a legitimate professional preparation which should be improved rather than circumvented. Six rationales for the validity of the above propositions, based on theory, logic, research, expert opinion, experience, and common sense, are detailed. In addition some historical perspective is provided regarding the use of teachers with and without professional education. (CB)