Considering how FFVI treats magic as an unnatural force, I would argue it's not some intrinsic force of the universe. At least not their universe, if we're going into baseless hypothetical metaphysics.

As far as we know, magic didn't exist until the Warring Triad came into the picture, so I have a hard time believing that magic is an intrisnic force of nature, that Espers and the Warring Traid simply made available. Granted, there is very little known about the VI world before the War of the Magi, even the world/character guide books start the timeline during the war, and says very little. So it is possible people knew about magic before the Warring Triad appeared but we'll never know.