Now let us ask ourselves what sort of identity of personality it is we are referring to when we say “when anything is seen, it is always I who see”. What is it I want all these cases of seeing to have in common? As an answer I have to confess to myself that it is not my bodily appearance. I don't always see part of my body when I see. And it isn't essential that my body, if seen amongst the things I see, should always look the same. In fact I don't mind how much it changes. And in the same way I feel about all the properties of my body, the characteristics of my behaviour, and even about my memories. ‒ ‒ ‒ When I think about it a little longer I see that what I wished to say was: “Always when anything is seen, something is seen”. I.e., that of which I said it continued during all the experiences of seeing was not any particular entity “I”, but the experience of seeing itself. This may become clearer if we imagine the man who makes our solipsistic statement to point to his eyes while he says “I”. (Perhaps because he wishes to be exact and wants to say expressly which eyes belong to the mouth which says “I” and
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to the hands pointing to his own body). But what is he pointing to? These particular eyes with the identity of physical objects? (To understand this sentence, you must remember that the grammar of words of which we say that they stand for physical objects is characterized by the way in which we use the phrase “the same so-and-so”, or “the identical so-and-so”, where so-and-so designates the physical object.) We said before that we did not wish to point to a particular physical object at all. The idea that he had made a significant statement arose from a confusion corresponding to the confusion between what we shall call “the geometrical eye” and “the physical eye”. I will indicate the use of these terms: If a man tries to obey the order “Point to your eye”, he may do many different things, and there are many different criteria which he will accept for having pointed to his eye. If these criteria, as they usually do, coincide, I may use them alternately and in different combinations to show me that I have touched my eye. If they don't coincide, I shall have to distinguish between different senses of the phrase “I touch my eye” or “I move my finger towards my eye”. If, e.g., my eyes are shut, I can still have the characteristic kinaesthetic experience in my arm which I should call the kinaesthetic experience of raising my hand to my eye. That I had succeeded in doing so, I shall recognize by the peculiar tactile sensation of touching my eye. But if my eye was behind a glass plate which was fastened in such a way that it prevented
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me from exerting a pressure on my eye with my finger, there would still be a criterion of muscular sensation which would make me say that now my finger was in front of my eye. As to visual criteria, there are two I can adopt. There is the ordinary experience of seeing my hand rise and come towards my eye, and this experience of course is different from seeing two things meet, say, two finger tips. On the other hand, I can use a criterion for my finger moving towards my eye, what I see when I look into a mirror and see my finger nearing my eye. If that place on my body which, we say, “sees” is to be determined by moving my finger towards my eye, according to the second criterion, then it is conceivable that I may see with what according to other criteria is the tip of my nose, or places on my forehead; or I might in this way point to a place lying outside my body. If I wish a person to point to his eye (or his eyes) according to the second criterion alone, I shall express my wish by saying: “Point to your geometrical eye (or eyes)”. The grammar of the word “geometrical eye” stands in the same relation to the grammar of the word “physical eye” as the grammar of the expression “the visual sense datum of a tree” to the grammar of the expression “the physical tree”. In either case it confuses everything to say “the one is a different kind of object from the other”; for those who say that a sense datum is a different kind of object from a physical object misunderstand the grammar of the word “kind”, just as those who say that a number is a different kind of
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object from a numeral. They think they are making such a statement as “A railway train, a railway station, and a railway car are different kinds of objects”, whereas their statement is analogous to “A railway train, a railway accident, and a railway law are different kinds of objects”.