This is Volume XVII of twenty-two in a series on 20th Century Philosophy. Originally published in 1959, it is a contribution to the History of Modern Philosophy under the heads: first of different Schools of Thought-Sensationalist, Realist, Idealist, Intuitivist; secondly of different Subjects-Psychology, Ethics, Aesthetics, Political Philosophy, Theology. This is a collection of papers by George Edward Moore, Emeritus Professor of Philosophy and Fellow of Trinity College in the University of Cambridge.