 (f) Constructive set theory (as do the theories under (d) and (e)) sets out to develop a framework for the style of constructive mathematics of Bishop’s 1967 Foundations of constructive analysis in which he carried out a development of constructive analysis, based on informal notions of constructive function and set, which went substantially further mathematically than anything done before by constructivists. Where Brouwer reveled in differences, Bishop stressed the commonalities with classical mathematics. What was novel about his work was that it could be read as a piece of classical mathematics as well.