A summary of today In order to argue about a topic (e.g. Is "America" good) your brain has to have a mental representation of America. For example, if Bob says "America is evil", then what Bob is actually saying is:
"I have some memory of America and I interpret this memory as EVIL."
Then when Tom counters with:
"But America is actually good. YOU'RE evil."
What Tom is actually saying is:
"I have some other mental representation of America. It differs from yours and I think you're wrong."
But if both Tom and Bob have different mental representations of America, doesn't that mean that each person is talking about a different America (but call it by the same name)? Tom is talking about Tom's representation of America and Bob is talking about Bob's mental representation of America. Since these representations are not the same, then in effect each person is talking about a 'different' America.
A broader question: Why do we assume that if two people use the same "words" they're thinking the same "concepts?"