This is a really nice article. It's well organized and explains things in a very clear and concise manner. I have only one minor quibble. You write about "factual" information (or data). Maybe I've been a social scientist too long, but I'm more inclined to phrase these ideas as "what we take to be factual..." Perhaps in natural sciences, engineering, business or industry that which "factual" is more concrete. I'm not suggesting you're in any way incorrect. Rather that "facts" are easier to come by in some disciplines than others. Great article. - Matty