Healing magic is... [Bruce trails off for a moment, lost in thought. The knowledge of it is right at his fingertips, of course - he may not use his magic, but that doesn't mean he's rusty or out of practice. He's dedicated a good chunk of his life learning about healing magic; that kind of knowledge doesn't just go away.

He brings up the hammer and shifts, eyeing the nail that's halfway into position and starts to hammer it down properly.] The human body naturally heals by itself, with enough given time. Healing magic usually just... encourages the process to quicken, and the magic itself gives the hastened healing the energy it needs to accomplish this.

[Pause as Bruce hammers one more time and pulls away from the fence he's working on.]

At least, that's the best estimate I can come up with. I could be entirely wrong, of course.