Gottlob Frege
…Principia Mathematica (3 vols., 1910–1913, by Bertrand Russell, 1872–1970, and Alfred North Whitehead, 1861–1947), to Russell's theory of descriptions, to Kurt Gödel's (1906–1978) incompleteness theorems, and to Alfred Tarski's (1901–1983) theory of truth, is ultimately due to Frege. One of Frege's stated purposes…