Abstract
I have long promoted the conjecture that expressing generality lies at the heart of school algebra. Indeed, I have gone further to suggest that ?a lesson without the opportunity for learners to generalise is not a mathematics lesson?. It seems beyond doubt that experiencing and expressing generality is natural to human beings. The pedagogic issue is why there is so much resistance amongst teachers and learners to using this power in mathematics lessons. The notion of generalisation here includes both abstraction from context and generalisation within context. Pondering this question has led us to wonder why generalisation happens sometimes and not others, what can be done to prompt useful mathematical generalisation, and under what sorts of circumstances: in short, what are the conditions for and evidence of imminent or proximal generalisation?
John Mason, Helen Drury and Liz Bills