We start with the existence of material objects. We can't know anything about what these are in themselves; all we have are sense-data. "This seems plainly absurd; but whoever wishes to become a philosopher must learn not to be frightened of absurdities." This sets the tone for the rest of the book, much of which is concerned with questions about knowledge in one way or another. How can we know anything and what does it mean to know anything anyway? Eventually we reach the question notoriously posed by Pontius Pilate: what is truth?
Much of the discussion centres on the difficult idea of universals, which Russell prefers to Plato's 'ideas' although the meaning is much the same. Universals belong to the world of being, which Russell distinguishes from the world of existence.
The world of being is unchangeable, rigid, exact, delightful to the mathematician, the logician, the builder of metaphysical systems, and all who love perfection more than life. The world of existence is fleeting, vague, without sharp boundaries, without any clear plan or arrangement, but it contains all thoughts and feelings, all the data of sense, and all physical harm, everything that makes any difference to the value of life and the world.Which of these worlds you prefer is largely a matter of temperament.
Although the book is quite short it contains a lot and needs to be taken slowly. Russell puts his finger on why philosophy is difficult for non-philosophers. "It is usually through particular instances that we come to be able to see the general principles. Only those who are practised in dealing with abstractions can readily grasp a general principle without the help of instances." Recognising this, Russell provides plenty of 'instances', but even so the reader has to work quite hard.
Many people are drawn to philosophy because they want to find answers to metaphysical questions about the meaning of life, the universe, and everything.
This hope, I believe, is vain. It would seem that knowledge concerning the universe as a whole is not to be obtained by metaphysics and that the proposed proofs that, in virtue of the laws of logic such and such things must exist and such and such others cannot, are not capable of surviving a critical scrutiny.In his concluding chapter Russell explains what he takes to be the value of the rather strange pursuit we call philosophy. Much of what used to be described under that heading has now been taken over by science, and this is a continuing trend; nevertheless a role for philosophy remains and it isn't trivial.
The value of philosophy is, in fact, to be sought largely in its very uncertainty. The man who has no tincture of philosophy goes through life imprisoned in the prejudices derived from common sense, from the habitual beliefs of his age or his nation, and from convictions which have grown up in his mind without the cooperation or consent of his deliberate reason. To such a man the world tends to become definite, finite, obvious; common objects rouse no questions and unfamiliar possibilities are contemptuously rejected.To such attitudes philosophy offers an alternative.
Philosophy, though unable to tell us with certainty what is the true answer to the doubts which it raises, is able to suggest many possibilities which enlarge our thoughts and free them from the tyranny of custom.This recalls what another philosopher, Galen Strawson, has said recently: "I think philosophy really does change one over time. It makes one's mind large in some peculiar manner."
In a bibliograpbical note at the end of the book Russell advises us to read what the great philosophers themselves have said rather than what others tell us they have said. I'm sure this is good advice and I wish I followed it more than I do.