 epsilon calculus |  Frege, Gottlob |  Gödel, Kurt: incompleteness theorems |  logic: second-order and higher-order |  logical pluralism |  model theory: first-order |  paradox: Skolem’s |  Peirce, Benjamin |  Peirce, Charles Sanders |  Peirce, Charles Sanders: logic |  proof theory: development of |  Russell, Bertrand |  Russell’s paradox |  set theory: Zermelo’s axiomatization of |  type theory |  Whitehead, Alfred North 