An explanation of the child's mind and his language, stated in terms of the nature of the learner, is presented in this book. The authors ask teachers to think about the competence of the child and try to discover what he must know to be able to read. They ask teachers to examine the nature of the learner--what he knows that enables him to learn to read and to read with comprehension. The book traces the development of the child as he gains competence first in thought, then in language, finally in reading by presenting research studies describing observed behavior and then offering theoretical explanations of that behavior. Finally, a series of hypotheses is offered to account for differences in performance with various materials and methods and competencies. The authors focus primarily on Piaget, Lenneberg, Chomsky, Vygotsky, and Underwood in their discussions. (TO)