Is there knowledge in the world that is so certain that no reasonable person could doubt it? Philosophy is the attempt to answer such fundamental questions, not carelessly and dogmatically, as we might in everyday life, but critically, after analyzing how and why the questions arise and clarifying the assumptions and concepts on which they are based. This classic work, first published in 1912, has never been replaced by an accessible introduction to the theory of philosophical inquiry. It conveys Russell's views on topics such as the difference between appearance and reality, the existence and nature of matter, idealism, knowledge by acquaintance and by description, induction, as well as the limits and value of philosophical knowledge. This edition includes an introduction by John Skorupski that contextualizes Russell's work, along with a guide to further reading.