jmartkdr2
Hero
To me, that falls under "knowing about magic." If they can reliably use it, because they understand how it works, it's not unknowable.I'm pretty flexible either way. I don't see it as a necessity for wizards to understand the underlying mechanics of magic to be able to cast spells or craft magic items, etc.
I would agree that whether the mechanics are knowable or not, societies would devote plenty of resources to make execution of magic more consistently effective. If it could be known, they'd try to know it. If it couldn't be known, they'd make records of what inputs were used and to what effects such that you'd have practical rules to follow to achieve the desired result.
Unknowable magic would have unpredictable resuts because you don't know any of the rules possibly because there are no rules.) But if you know that combining these ingredients, saying these words and making these gestures make a fireball: you know about magic. If you know about magic and how to use it, it cannot be unknowable.
edit: All the above assumes that knowable or not, the output of the magic is more valuable than the resources used to achieve it.