The purpose of this Forum is to stimulate critical debate in the area of theory use and
theory development, and to consider future directions for the advancement of our
discipline. The Forum opens with a discussion of why theories are essential to the
work of mathematics educators and addresses possible reasons for why some
researchers either ignore or misunderstand/misuse theory in their work. Other issues
to be addressed include the social turn in mathematics education, an evolutionary
perspective on the nature of human cognition, the use of theory to advance our
understanding of student cognitive development, and models and modelling
perspectives. The final paper takes a critical survey of European mathematics
didactics traditions, particularly those in Germany and compares these to historical
trends in other parts of the world.