Quote Originally Posted by raz View Post
It's more like a playing field. To an E, the external world is their playground. To an I, their inner thoughts are where home is. That's the simplest way to put the difference. You're going to be draining yourself by devoting time to the playing field you don't focus on.

Plus there's also the fact that when you extravert or introvert, you can be faced against one of 4 functions. This is more easily noticed in extraversion as when you contend with the outside world, you have trillions of people that are altering it. You might extravert with intuition, but if you're having to use your intuition to deal with something thinking oriented, it's going to be more taxing.
Yeah this sounds much closer to the idea of extroversion and introversion than most other things. Si for instance is not the function that focuses on the external world, but it is still based upon realism and actuality. It is one's thoughts and memories that propel their sense of regularity and confidence, which makes this dominant function user more obstinate but still focused on reality.