Published online by Cambridge University Press: 12 March 2014
In intuitionistic mathematics one distinguishes between sets with a constructive character and sets in a more general sense. The first kind consists of spreads and the latter of species. The definition of a spread utilizes so-called choice sequences (in [5] infinitely proceeding sequence or ips), i.e., sequences of well-determined mathematical objects which are chosen more or less freely. One can restrict the choices by some law, which, however, need not be predetermined (changing one's mind is allowed).
This research was supported in part by National Science Foundation grant GP-4361.
Part of the material has for the first time been presented at a seminar at the Massachusetts Institute of Technology.