A Wittgensteinian Fragment on Solipsism and the Self

According to Wittgenstein, the solipsist is contradicting himself when he says, "Only what I see exists." That's because the I/self itself isn't seen in experience. Therefore, like the rest of the things he doesn't see, he has no right to talk about the I/self at all.

As Quine also said, if we have no “criterion of identity” for an object, then we should deny that object any (official) existence. Thus the I/self has no criterion of identity and therefore it should be thrown overboard.

The solipsist doesn't exist by his own standards because the I isn't seen, only the things that the I sees are seen. Thus the subject is indeed “a vanishing point” (Tractatus). There's nothing to see, hear, or smell; but that which the I itself sees, hears and smells. Thus perhaps we should write the I/self in quotation marks because it can be taken as a word without a referent or designation.

What is a person? 

Is it something over and above (to use David Pears' words) “the subject which is living this mental life” or “the subject which is having these visual impressions”? Surely some thing needs to have a mental life or have visual impressions. Or do we just intuitively presume that there needs to be a subject of a mental life or a subject of visual impressions?

Instead of the word 'person', we now meet the word 'subject'; which doesn't seem identical. A subject is a subject of something whereas a person needn't be the subject of something. (At least this is the case on certain readings of the concept [person].)

What is a subject? 

Subjects in subject-predicate expressions are the subjects of predication. Can we predicate anything of the subject? We can predicate experiences or cognitive operations of the subject. For example, when I say "The rose is red", I'm predicating an attribute (or property) of the rose. However, experiences or cognitive operations aren't the same kind of predicate as “red”. These are things the subject does or carries out. The rose, on the other hand, doesn't do red, carry out red or experience red. (This is like saying “John works on the farm” rather than “John is tall”.) Do we have predicates of the latter kind which can be predicated of the subject? We can say what the subject does or what the subject experiences; though can we attribute properties to the subject? It's these kinds of criteria of identity that are missing from the subject. No; the subject has no intrinsic identity-conditions. However, if the subject has vanished, then how can it be the subject of experiences or of cognitive operations? Something must surely experience things and carry out cognitive operations.