Currently, after years of not playing using D&D 3.5, I am planning magic-heavy campaing. Basically each player will have to play caster class (no mundane fighters or rogues), so I wanted to refresh my knowledge to present all possible character creation options to my players. I also want to come up with some theory of magic for my setting. I want it to be coherent with sourcebooks. However, this is not the main subject of my question.
D&D 3.5 Core Books describe 2 types of magic: arcane and divine. The source of the former are mystic energies, for the latter they are divine sources.
I already have some issues with this model. I understand how wizard and sorcerer are arcane casters, and cleric is divine caster. However, what bard's music has to do with arcane magic, and what druid's devotion to nature or paladin's devotion to law has to do with deity-granted powers?
I have also checked some more supplemental books, and it turns out that there are even more types. Instead of 2, there are now 8 or maybe even more:
Are those new types a subtypes of divine/arcane magic or completely separate sources of power? Eg. Isn't the pact magic same as divine magic, but instead of deity, cleric has Cthulhu-like entity as her patron?
My question is:
How do different types of magic sources described in various sourcebooks relate to each other?
Naturally, I am looking only for answers based on official sourcebooks. I am probably able to come up with something to explain it in my setting, but maybe it has been already explained in official sources.