In the description so far, the place where elementary mathematical thinking becomes
advanced has yet to be precisely defined. In figure 1, the “transition to advanced
mathematics” includes systematic Euclidean geometry, calculus and advanced algebra.
Certainly these subjects all involve inherent difficulties requiring considerable cognitive reconstruction and, at various times in history (ancient Greece, the seventeenth and nineteenth centuries, respectively), they were topics of mathematical research by the most creative minds of their generation. Calculus and advanced algebra also contain a significant quantity of the mathematics taught at university for students as service subjects, so it would be politic to include these subjects as “advanced mathematics”.