In the deliberations of the Advanced Mathematical Thinking Group of PME at its first
meeting in 1987, we found it impossible to come to an agreement and decided
pragmatically to take our brief to study mathematical thinking in topics beyond regular
mathematics from the age of sixteen. Pragmatism suggests that it would be pertinent to
include Euclidean geometry, calculus and advanced algebra above the line. However,
whereas each of these subjects has its own idiosyncratic difficulties, the universal
cognitive change occurs with the introduction of the axiomatic method, where
mathematical objects have a new cognitive status as defined concepts constructed from