Philosophy

by Bertrand Russell

If this is correct, what really happens when, as common sense would say, we are conscious of a table, is more or less as follows. First there is a physical process external to the body, producing a stimulus to the eye which occurs rarely (not never) in the absence of an actual physical table. Then there is a process in the eye, nerves, and brain, and finally there is a coloured pattern. This coloured pattern, by the law of association, gives rise to tactual and other expectations and images; also, perhaps, to memories and other habits. But everything in this whole series consists of a causally continuous chain of events in space-time, and we have no reason to assert that the events in us are so very different from the events outside us—as to this, we must remain ignorant, since the outside events are only known as to their abstract mathematical characteristics, which do not show whether these events are like “thoughts” or unlike them.

It follows that “consciousness” cannot be defined either as a peculiar kind of relation or as an intrinsic character belonging to certain events and not to others. “Mental” events are not essentially relational, and we do not know enough of the intrinsic character of events outside us to say whether it does or does not differ from that of “mental” events. But what makes us call a certain class of events “mental” and distinguish them from other events is the combination of sensitivity with associative reproduction. The more markedly this combination exists, the more “mental” are the events concerned; thus mentality is a matter of degree.

There is, however, a further point which must be discussed in this connection, and that is “self-consciousness”, or awareness of our own “mental” events. We already had occasion to touch on this in [Chapter XVI] in connection with Descartes’ “I think, therefore I am”. But I want to discuss the question afresh in connection with “consciousness”.

When the plain man sees “a table” in the presence of a philosopher, the plain man can be driven, by the arguments we have repeatedly brought forward, to admit that he cannot have complete certainty as to anything outside himself. But if he does not lose his head or his temper, he will remain certain that there is a coloured pattern, which may be in him, but indubitably exists. No argument from logic or physics even tends to show that he is mistaken in this; therefore there is no reason why he should surrender his conviction. The argument about knowledge in [Chapter VIII] showed that, accepting the usual views of physicists as to causal laws, our knowledge becomes more certain as the causal chain from object to reaction is shortened, and can only be quite certain when the two are in the same place in space-time, or at least contiguous. Thus we should expect that the highest grade of certainty would belong to knowledge as to what happens in our own heads. And this is exactly what we have when we are aware of our own “mental” events, such as the existence of a coloured pattern when we thought we were seeing a table.

We might, therefore, if we were anxious to preserve the word “mental”, define a “mental” event as one that can be known with the highest grade of certainty, because, in physical space-time, the event and the knowing of it are contiguous. Thus “mental” events will be certain of the events that occur in heads that have brains. They will not be all events that occur in brains, but only such as cause a reaction of the kind that can be called “knowledge”.

There are, however, still a number of difficult questions, to which, as yet, a definitive answer cannot be given. When we “know” a thought of our own, what happens? And do we know the thought in a more intimate way than we know anything else? Knowledge of external events, as we have seen, consists of a certain sensitivity to their presence, but not in having in or before our minds anything similar to them, except in certain abstract structural respects. Is knowledge of our own minds equally abstract and indirect? Or is it something more analogous to what we ordinarily imagine knowledge to be?

Take first the question: What happens when we “know” a thought of our own? Taking the definition of “knowing” that we adopted in [Chapter VIII], we shall say: We “know” a thought of our own when an event in our brain causes a characteristic reaction which is present when the event occurs and not otherwise. In this sense, whenever we say, “I see a table”, we are knowing a thought, since an event in our brain is the only invariable antecedent of such a statement (assuming it to be made truthfully). We may think we are knowing a table, but this is an error.

Thus the difference between introspective and other knowledge is only in our intention and in the degree of certainty. When we say, “I see a table”, we may intend to know an external object, but if so we may be mistaken; we are, however, actually knowing the occurrence of a visual percept. When we describe the same occurrence in the words “a certain coloured pattern is occurring”, we have changed our intention and are much more certain of being right. Thus all that differentiates our reaction when it gives introspective knowledge from our reaction when it gives knowledge of another kind is the elimination of a possible source of error.

I come now to the question: Do we know our own thoughts in a more intimate way than we know anything else? This is a question to which it is difficult to give precision; it describes something that one feels to be a problem without being able to say exactly what the problem is. However, some things can be said which may serve to clear up our feelings, if not our ideas.

Suppose you are asked to repeat after a man whatever he says, as a test of your hearing. He says “how do you do?” and you repeat “how do you do?” This is your knowledge-reaction, and you hear yourself speaking. You can perceive that what you hear when you speak is closely similar to what you hear when the other man speaks. This makes you feel that your reaction reproduces accurately what you heard. Your knowledge-reaction, in this case, is the cause of an occurrence closely similar to the occurrence that you are knowing. Moreover, our inveterate naive realism makes us think that what we said was what we heard while we were speaking. This is, of course, an illusion, since an elaborate chain of physical and physiological causation intervenes between speaking and hearing oneself speak; nevertheless, the illusion re-enforces our conviction that our knowledge, in such a case, is very intimate. And it is, in fact, as intimate as it can hope to be, when our knowledge-reaction reproduces the very event we are knowing, or at least an event extremely similar to it. This may be the case on other occasions, but we can only know, with any certainty, that it is the case when what is known is a percept. This accounts for the fact that our most indubitable and complete knowledge is concerning percepts, not concerning other mental events or events in the external world. Our reaction to a sound can be to make a similar sound, and if we are clever enough we can paint something very like what we see. But we cannot show our knowledge of a pleasure by creating for ourselves another very similar pleasure, nor of a desire by creating a similar desire. Thus percepts are known with more accuracy and certainty than anything else either in the outer world or in our own minds.