In short, you mean you do not like the idea of using "physical" and "spiritual"? Okay, I can see your point.
It still is a little confusing, though, using "Internal" and "External." When I first came across the terms, anyway, I figured they were just another way of saying "Introversion" and "Extroversion," so I'm sure many others have probably confused the two as well.
Maybe the least confusing terms would be "Observable" and "Invisible" or something like that...
Bah, now this thread has turned into a semantics discussion...oh well.