Thanks for your response.Yes, by 'experience' I mean 'see', as vision seems to provide the best arena for testing determinable experience. The point I am trying to make can be illustrated by an example. Say you and I are looking at an apple and this particular apple has a very uncharacteristic white spot about 10 mm in diameter on its skin. I can point to the white spot that I see there and confidently predict that when I ask you what you see there, you will report seeing the white spot. This kind of thing is apparently pretty much a universal human experience. I can point to any feature in the visual environment, ask you to describe it, and if you are sane and of good will enough to give a truthful report of what you see, I can be nearly certain that your description will recognizably match what I see. Now since your perceptions are not determined by mine and vice versa, what do you think is the most plausible explanation for this invariance when it comes to detailed particulars? Or, alternatively, what are the possible explanations you can think of?
You say that there is no evidence that we both see the same particulars.I think that assertion flies in the face of common experience and I think the example I gave shows this clearly. If you don't agree, please explain exactly why.
Can I just put one fact right first. I said there is no evidence to show in my brain or optical array that I am perceiving even a single object. I am looking at a computer screen at the moment but there is no evidence to show that this is actually the case.
You say that common sense experience 'flies in the face' of any epistemological doubt that what we actually observe is true. But though we all share the same experience of the apple, say, or the table, this would not mean common sense alone is evidence that the apple or table exists in the world. If I said to another person 'That is an apple' and the other person agrees it is, then we have to face the sceptical claim that the description of something is not what is described. We do not have knowledge of the world, only understanding.
You ask for a possible explanation of why two, or any number of descriptions of a shared object should match. In the case of later Wittgenstein this is a language game. Primitively, we have only agreed upon calling an apple an apple and a table a table, which can be true or false in the world, depending upon whether you are a realist or not. If you are a realist then you have to show how the meaning is determined. Wittgenstein's earlier philosophy (in the Tractatus), which has to be viewed in the light of the later philosophy of his Investigations, says a proposition or a sentence like 'That is an apple' is a simple (atomic) claim between what is described and the description. We are not talking about 'objects' as such that we normally believe we perceive, like the apple, only the primitive psychological 'object' and the primitive 'object' in the world.
When two or more persons agree the apple they are perceiving has a white spot, it is only an agreement, not knowledge of the world. It cannot be demonstrated that they have agreed upon the same thing in the world. When two or more persons agree upon calling an apple an apple then that is simply a semantic agreement, unless it can be shown to be more than this. Let's say Robinson Crusoe on an island calls the monkeys he observes, and which he has not seen before, 'moneyskees'. Let's say, further, that another person is washed ashore and Crusoe says of the monkeys, they are 'moneyskees.' The second person agrees and so monkeys are 'moneyskees'. There has been no change in the world, only in how we describe it.
I hope this clear.