First of all, I don't think that anyone has yet pointed to the useful (lengthy!) Wikipedia article on
Theory of Mind. There are still folks who turn their noses up at Wikipedia references, but I usually find them to give quite useful background information for discussion topics.
One of the great linguists of the 20th century, Charles Fillmore, passed away recently. He was my mentor when it came to lexical semantics. A few years ago, I met him at an ACL conference in Montreal, and he gave me a definition of language that still resonates deeply with me--Language is
word-guided mental telepathy.
Well, if you understand Frame Semantics, you know where he is coming from, but I was very familiar with his thinking since my undergraduate days. He had been my advisor when I was an undergraduate linguistics major at Ohio State University. And he had been profoundly affected by Roger Schank's contribution to discourse understanding. He always approached language in terms of its relationship to a conceptual framework. So it makes sense to think of language as catalysis for the blending of two separate trains of thought. The deeper question, I suppose, is how we ought to think of a "train of thought". What does it consist of?