This book was first published in 1979. The authors' examinePiaget's Theory starting by considering and commenting on the kinds of question one must ask of a scientific theory. None of the questions demands an absolute answer. Theories are judged in some respects with reference to competing theories. In other respects they are judged against our sense of scientific progress. In subsequent chapters the authors' look at Piaget's theory in detail with such issues in mind. They also endeavour to locate Piaget's theory in the context of other views of intellectual development. In that section we focus on the issue we first nominated, that is the problem of making choices about the kinds of question to ask and the kinds of data to select.