A number of researchers are developing a constructivist theory of mathematics learning, including Paul Cobb, Ernst von Glasersfeld and Les Steffe (see, for example, Cobb and Steffe, 1983; Glasersfeld, 1987; Steffe, Glasersfeld, Richards and Cobb, 1983). As they appear to have rejected many of the problematic aspects of Piaget’s work, such as his stages, much of their theory can be seen as parallel to social constructivism, on the psychological plane. However it is not clear that all of their auxiliary assumptions, such as those involved in accounting for young children’s number acquisition, are fully compatible with social constructivism.