Well, whether or not you can perform magecraft is determined from the moment of your birth based on the magic circuits embedded in your soul and reflected on your body. You channel magical energy or prana through these circuits to perform spells. The goal of magecraft is to replicate miracles and ultimately reach the root, but it can also be used for more mudane things like combat.

[Bazett is part of the second category.]

And yet there are things that even magecraft cannot do, like create sentient dolls without recycling souls.