In contemporary philosophy, most Platonists trace their ideas to Gottlob Frege's influential paper "Thought," which argues for Platonism with respect to propositions, and his influential book, "The Foundations of Arithmetic", which argues for Platonism with respect to numbers and is a seminal text of the logicist project. Contemporary analytic philosophers who espoused Platonism in metaphysics include Bertrand Russell, Alonzo Church, Kurt Gödel, W. V. O. Quine, David Kaplan, Saul Kripke, Edward Zalta and Peter van Inwagen. Iris Murdoch espoused Platonism in moral philosophy in her 1970 book "The Sovereignty of Good".