In Dresden Files, he goes on about how you can't "create" energy. So he does stuff like freeze water by taking the heat out of it and shooting it off into the sky, or whatever. And when he doesn't do that, the fire energy comes from his "will."

Which is all well and good, but I'm glad it doesn't try to justify anything else. It's magic, you CAN'T justify it with physics.

WoT does something similar, with flying. Everyone acts as if it's the height of insanity to try to fly with the Power- it's like trying to fly by pulling up on your boots. Except... that makes no sense. Weaves of Air don't have the same action/reaction on people. If Elayne lifts up a bus and throws it down the street with Air, she doesn't get tossed back in the opposite direction.

It comes from people trying to make their magic systems internally consistent- an admirable goal, IMO, but it's never going to QUITE work.