Designing a contractual magic system?

[Apollonian]

Originally Posted by dataweaver

The distinctions don't have to be fuzzy, any more than the distinction between a dog and a cat or a dog and a man is fuzzy. But the original poster did ask for essentially a unified system wherein “everything from clerics to wizards are following the same rules but they are all doing it in different ways because they have different social agreements”.

This is an attempt to address that, with the added caveat that what you're contracting with should say something about what kind of contract you form, and vice versa: a shaman attempting to bargain with a god will likely get punished for his hubris; and attempting to bargain with the spiritual equivalent of a dog will just be ineffective. A sorcerer who attempts to treat the sorts of spirits that a shaman deals with in the way he deals with the “dog-like” spirits that are his usual purview is engaging in a form of slavery; attempting to do that to a god is just plain stupid. It's entirely appropriate for a priest to serve a god; it is not appropriate to serve anything less than a god.

So priests serve gods, shamans bargain with sapient spirits, and sorcerers command non-sapient spirits. There are exceptions to these three pairings; but those exceptions are foolish or evil or both. The evil ones are suitable for villains but not heroes; the foolish ones are only suitable for the village idiot.

And yes, within each of these broad categories, you can have different types, such as human, demonic, fae, alien, etc. You can blur the boundaries among them if you wish; or you can make the boundaries sharp and distinct.

There's an implication here of a cosmic hierarchy, which calls to mind a Celestial Bureaucracy that maintains the records and paperwork that keep that hierarchy in place. A natural adventure would, of course, be infiltrating said bureaucracy so you can alter the records to your benefit... Likewise, all these bargains, supplications, and commands must follow the correct forms. Law (Spirits) is a prerequisite skill for any magic worker. (I don't think that's what you're aiming for, but it struck me as a neat way to build off of the idea.)