I had a complicated point to make about the interplay of vocabulary and simplifying ideas in order to make thinking more clear (and thus perhaps rationality?) but I think I kind of lost that in the post and have made it sound more like "can people think if they don't have words?".

I agree with what you've written, and I'd say that your last sentence rather answers my (intended) question: correlation may exist, but causation is a lot trickier to pin.