to be external perception, but this is concealed by precarious extensions into the physical world. I think introspection, on the contrary, involves precarious extensions into the mental world: shorn of these, it is not very different from external perception shorn of its extensions. To make this clear, I shall try to show what we know to be occurring when, as we say, we think about philosophy.
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
