Suppose, as the result of introspection, you arrive at a belief which you express in the words: “I am now believing that mind is different from matter”. What do you know, apart from inferences, in such a case? First of all, you must cut out the word “I”: the person who believes is an inference, not part of what you know immediately. In the second place, you must be careful about the word “believing”: I am not now concerned with what this word should mean in logic or theory of knowledge; I am concerned with what it can mean when used to describe a direct experience. In such a case, it would seem that it can only describe a certain kind of feeling. And as for the proposition you think you are believing, namely, “mind is different from matter”, it is very difficult to say what is really occurring when you think you believe it. It may be mere words, pronounced, visualised, or in auditory or motor images. It may be images of what the words “mean”, but in that case it will not be at all an accurate representation of the logical content of the proposition. You may have an image of a statue of Newton “voyaging through strange seas of thought alone”, and another image of a stone rolling downhill, combined with the words “how different!” Or you may think of the difference between composing a lecture and eating your dinner. It is only when you come to expressing your thought in words that you approach logical precision. Both in introspection and in external perception, we try to express what we know in WORDS. We come here, as in the question of testimony, upon the social aspect of knowledge. The purpose of words is to give the same kind of publicity to thought as is claimed for physical objects. A number of people can hear a spoken word or see a written word, because each is a physical occurrence. If I say to you, “mind is different from matter”, there may be only a very slight resemblance between the thought that I am trying to express and the thought which is aroused in you, but these two thoughts have just this in common, that they can be expressed by the same words. Similarly, there may be great differences between what you and I see when, as we say, we look at the same chair; nevertheless we can both express our perceptions by the same words. A thought and a perception are thus not so very different in their own nature. If physics is true, they are different in their correlations: when I see a chair, others have more or less similar perceptions, and it is thought that these are all connected with light-waves coming from the chair, whereas, when I think a thought, others may not be thinking anything similar. But this applies also to feeling a toothache, which would not usually be regarded as a case of introspection. On the whole, therefore, there seems no reason to regard introspection as a different _kind_ of knowledge from external perception. But this whole question will concern us again at a later stage.