ABSTRACT
In this chapter, we shall seek an answer to two questions: First, how do we know about the world dealt with in physics? Secondly, what do we know about it, assuming the truth of modern physics?
First: How do we know about the physical world? We have already seen that this question cannot have a simple answer, since the basis of inference is something that happens in our own heads, and our knowledge of anything outside our own heads must be more or less precarious. For the present, I shall take it for granted that we may accept testimony, with due precautions. In other words, I shall assume that what we hear when, as we believe, others are speaking to us does in fact have ‘meaning’ to the speaker, and not only to us; with a corresponding assumption as regards writing. This assumption will be examined at a later stage. For the present, I will merely emphasise that it is an assumption, and that it may possibly be false, since people seem to speak to us in dreams, and yet, on waking, we become
persuaded that we invented the dream. It is impossible to prove, by a demonstrative argument, that we are not always dreaming; the best we can hope is a proof that this is improbable. But for the present let us leave this discussion on one side, and assume that the words we hear and read ‘mean’ what they would if we spoke or wrote them.
