 category theory |  continuity and infinitesimals |  Dedekind, Richard: contributions to the foundations of mathematics |  Frege, Gottlob |  Hilbert, David: program in the foundations of mathematics |  paradoxes: and contemporary logic |  Principia Mathematica |  Russell, Bertrand |  Russell’s paradox |  set theory |  set theory: continuum hypothesis |  set theory: Zermelo’s axiomatization of |  Whitehead, Alfred North 