This is kind of a hard question to ask. I'm doing some research on the human mind and its attributes - learning, thinking, etc.
There are many different kinds of thinking/reasoning, and I'd like to put together a basic classification. It's confusing, because psychologists, physiologists, philosophers and others all have different approaches.
Anyway, consider the following: Science, Philosophy, Religion, Spirituality
These are examples of what? For example, you could say that science and philosophy are overlapping "thinking spheres." I wouldn't call them "knowledge spheres," because philosophy isn't dependent on hard facts, of course.
There's probably a common term that fits here, but I just can't think of it.
EDIT: I wrote "common word" in my original post but should have wrote "common term" instead.
Don't shoot me, but I chose lens over discipline (the answer with the most upvotes). In fact, neither answer is exactly what I was looking for. Discipline sounds a little too rigid when some of the "things" I seek to categorize can be hard to define (e.g. spirituality). On the other hand, lens, by itself, doesn't really work.
Then I went back and reread 1006a's answer and noted the term disciplinary lens, combining both words.
I asked a really tough, somewhat ambiguous, question, and I got a lot of good tips from all the answers.