Hello, I've come the conclusion that this is canon. That these branches are set aside from each other and have no link between them in any shape or form.
This quote describe my current standpoint on all this because it seems to make a lot of sense.
Like e.g. a necromancer is in fact a being that control the... arcane to manipulate life force and therefor it has nothing to do with e.g. fel energies which a warlock control or nature magic... stuff... druids control.
Another example: A mage who make a fireball can do it in two ways either he/she/it use the arcane to manipulate the raw form of fire, or commune with the elemental spirits for the ability(which could be done in many ways).
So in short words we have these 5 forces which people choose to control in order to do stuff?
and they have nothing to do with eachother.
How much wrong am I?