

A constructive morse theory of sets
pp. 61-79
in: Dimiter G. Skordev (ed), Mathematical logic and its applications, Berlin, Springer, 1987Abstract
the primary concern … is number, and this means the positive integers … Everything attaches itself to number, and every mathematical statement ultimately expresses the fact that if we perform certain computations within the set of positive integers, we shall get certain results. [2, pp. 2–3]