 Bolzano, Bernard |  Carnap, Rudolf |  Church-Turing Thesis |  empiricism: logical |  lambda calculus, the |  logic: connexive |  logic: intensional |  logic: second-order and higher-order |  logical pluralism |  model theory |  paradox: Skolem’s |  Principia Mathematica |  Principia Mathematica: notation in |  quantum theory: quantum logic and probability theory |  truth values |  Turing machines |  type theory: Church’s type theory 