"Differences arise in language, and not in relations to reality," you write. This is a powerful way of looking at the language / world "problem," I think. With my students in Imagining Science I've been working through a few of the problems associated with that other dualism, mind / body. Basically, I want to challenge their shallow & automatic acceptance of the cogito. My own way out of Descartes begins with seeing mind as extensive & socially constructed, which may be to say (I'm not sure) that mind is a function of language. But even this move runs up eventually against Dr. Johnson's refutation of Berkeley: Asked how he could refute Berkelian idealism, the good doctor replied, "I refute it thus!" & kicked a large stone lying in the street. However one defines mind, there will always be the conditions of existence, aka the stone in the street.

You've given me so much to think about I find myself replying to one sentence at a time. More anon.