 category theory |  connectives: sentence connectives in formal logic |  Curry’s paradox |  Hilbert, David: program in the foundations of mathematics |  logic, history of: intuitionistic logic |  logic: classical |  logic: intuitionistic |  logic: linear |  logic: substructural |  logical constants |  mathematics, philosophy of: intuitionism |  paradoxes: and contemporary logic |  proof theory: development of |  realism: challenges to metaphysical |  Russell’s paradox |  self-reference |  truth: revision theory of |  type theory 