Neonchameleon
Legend
That's your preferred interpretation of how magic works. I don't see it myself, because then it means any monster with a magical attack (like, say, a Will O'Wisp) has to be knowledgeable in order to be able to do this thing repeatedly.
Um... isn't that the difference between a Spell and a Spell Like Ability? (In the case of a Will O'Wisp it's simply an extraordinary ability not even Supernatural, let alone Spell Like).
I much prefer the idea of always-accessible magic being an innate feature rather than learned. Simply for balance purposes, your Wizard can never know every spell, which to me isn't knowledge, but tricks, he can perform a few tricks. The book-learner can truly access all knowledge, but he'll never be able to do this without exercising his mind.
This makes no sense to me given how specialised modern scientists have to be. Actually mastering something and being able to control it on the fly is very different from being a diletante.