„If we compare. e. g. the systems of classical mathematics and of intuitionistic mathematics, we find that the first is much simpler and technically more efficient, while the second is more safe from surprising occurences, e. g. contradictions. At the present time, any estimation of the degree of safety of the system of classical mathematics, in other words, the degree of plausibility of its principles, is rather subjective. The majority of mathematicians seem to regard this degree as sufficiently high for all practical purposes and therefore prefer the application of classical mathematics to that of intuitionistic mathematics. The latter has not, so far as I know, been seriously applied in physics by anybody.“
— Rudolf Carnap German philosopher 1891 - 1970
Rudolf Carnap (1939; 51), as cited in: Paul van Ulsen. Wetenschapsfilosofie http://www.illc.uva.nl/Research/Publications/Inaugurals/IV-10-Arend-Heyting.text.pdf, 6 november 2017.