As has been the case in medicine, social work, and psychiatry, progress in education will follow closely the adequacy of our category system concerning pertinent functions of a child, our understanding of these functions, how children fail to function properly (malfunction), causes of malfunction, signs of malfunction, course of malfunction (time, sequence, and states), means of detection, and the development of techniques specific to a task. The more we understand our task, the more we can direct our efforts. Not only is such information necessary to classroom diagnosis and prescription, but it also serves to direct research and development efforts. A study of the literature in these other applied sciences to determine the types of background knowledge a practitioner in these professions requires in order to provide appropriate treatments for his clientele reveals, among other things, the fact that these professions emphasize diagnostic information more than does education, the practitioner's first task being to arrive at a systematic understanding of his client so that he can focus his efforts more effectively. If individualization of instruction implies that the teacher's task is to provide experiences appropriate to each child's present level of development, potential, interests, etc., then a similar approach is needed for progress in education. (JS)