The Problems of Philosophy (1912) is one of Bertrand Russell's attempts to create a brief and accessible guide to the problems of philosophy. Focusing on problems he believes will provoke positive and constructive discussion, Russell concentrates on knowledge rather than metaphysics: If it is uncertain that external objects exist, how can we then have knowledge of them but by probability. There is no reason to doubt the existence of external objects simply because of sense data.Russell guides the reader through his famous 1910 distinction between "knowledge by acquaintance and knowledge by description" and introduces important theories of Plato, Aristotle, René Descartes, David Hume, John Locke, Immanuel Kant, G. W. F. Hegel and others to lay the foundation for philosophical inquiry by general readers and scholars alike.