chapter  4
Sense-data and the Anti-private Language Argument
Pages 28

We have seen how the traditional arguments for sense-data can be resisted. The supposed coup de grâce against the theory is provided by an attempt to prove that, whatever the arguments for sense-data, there just could not be such things. Sense-data, at least as usually conceived, are not public objects in public space, but are necessarily private to individual observers. They are what have come to be called logically private objects. The final crisis for the empiricist conception of perception was precipitated by Wittgenstein’s famous polemic against such private objects. He argued that such things could not be objects of linguistic reference and, hence, not objects of thought or consciousness.