To this very day, the chaotic weave of magic is a mystery to us. There are the well known stories of Mystra and her influence on our understanding of it, but in many ways, it’s just a force of destruction, that we can somehow wield as a mutated arm of our extended spirit. It’s accepted theory that the art of learning arcane secrets - taming these forces of magic, was brought to us as a gift from the elves when they originally migrated to our lands. Something they learned from Mystra.
But, it was not the elves who created these powers, or Mystra. It is theorized that it came in a great sudden surge of power, not unlike the collision, if only much more concentrated and subtle around the time of the Betrayal of Eos. Something allowed this great force to break through onto our plane, and it changed everything. But still, from where it came, we can only ponder...
A lecture on the history of arcana, Lopp'aris Polymoris, 642 AE, the third age.