Is there any knowledge in the world which is so certain that no reasonable man could doubt it?' Philosophy is the attempt to answer such ultimate questions, not carelessly and dogmatically, as we might deal with them in ordinary life, but critically, after analysing 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 supplanted as an approachable introduction to the theory of philosophical enquiry. It gives Russell's views on such subjects as the distinction between appearance and reality, the existence and nature of matter, idealism, knowledge by acquaintance and by description, induction, and the limits and value of philosophical knowledge. This edition includes an introduction by John Skorupski contextualizing Russell's work, and a guide to further reading.