The whole notion of a "culture of the mathematics classroom" implies an acceptance of the idea that mathematics exerts a unique influence on the context of classrooms in which the subject is being taught and learned. This is a relatively recent departure from traditional concerns in mathematics education and is one of the outcomes of shifts in perspectives within the field that have, in turn, given rise to some changes of emphasis in related research. A book such as this is in itself indicative of the importance given to new considerations of this kind. The aim of this chapter is to provide a theoretical setting for the chapters that follow which are concerned, in one way or another, with issues related to this change. In attempting to provide this setting, changes will be viewed from three broad perspectives: (a) those related to the nature of mathematics as a discipline; (b) those concerned with research about teachers and the teaching of mathematics, and (c) those concerning pupil perspectives.