 descriptions |  Frege, Gottlob |  Gödel, Kurt |  knowledge: by acquaintance vs. description |  logic: classical |  logical atomism: Russell’s |  logical constructions |  logicism and neologicism |  mathematics, philosophy of |  Moore, George Edward |  neutral monism |  Principia Mathematica |  Principia Mathematica: notation in |  propositional function |  Russell, Bertrand: moral philosophy |  Russell’s paradox |  type theory |  Whitehead, Alfred North |  Wittgenstein, Ludwig 