L.E.J. Brower in action: blackboard, chalk, Lizst hair, Nehru jacket
... the intuition of two-oneness, the basal intuition of mathematics, creates not only the numbers one and two, but also all infinite ordinal numbers, inasmuch as one of the elements of the two-oneness may be thought of as a new two-oneness, which process may be repeated indefinitely...*this comes from L.E.J. Brower, one of the most important mathematicians of the 20th century and defender of contructivism in mathematics. Reading Brower is like tripping on set theory.
*Benacerraf P. and Putnam H. (eds) (1983) Philosophy of Mathematics, 2nd edition, (Cambridge: Cambridge University Press). p. 80