Help me make a magic system that doesn't suck

I have a love/hate relationship with magic systems in role playing games. I haven't had to worry about using a magic system in my last few campaigns because we were playing in a very low magic world. The campaign I am currently working on is going to be a standard fantasy world where magic is relatively prevalent, and this raises the irritating question of what kind of magic system do I want to use.

The game system I'm using is going to be a stripped down d20 (no feats or powers, or 4e generally) with a mingling of old school AD&D thrown in for colour. I would love to have my own game system up and running, but time and wanting to actually play are outweighing that project so it can simmer on the back burner for a while longer.

You might be wondering why I'm not using D&D's magic system, and the answer would be, I fucking hate D&D's magic system, and always have. I might lose old school cred (I don't think I have any anyways) for that statement, but who cares. D&D's magic system will not fit what I'm looking for, and unfortunately I don't think anything will. I need a completely original system, and that's where you come in.

I need help designing a magic system, obviously. If you have any cool or insightful ideas I would love to read them. If you help me I can offer lots of gratitude and praise, but not much else. But you will have the satisfaction of knowing that a fellow GM thinks your idea is awesome and is going to use it in his game.

I have four criteria that I want the magic system to meet:

1. The magic must make sense.
I know this sounds silly, it is magic after all, but knowing how magic works and why is very important. Who can use magic, and what is its relationship to the world and the worlds physics etc... these all have to make sense and be translatable into game terms.

2. Magic has to be more than just spells.
What is the philosophy of magic and why is it used. I don't want a magic system that is only a series of progressive spells and nothing more, it has to be more meaningful than that.

3. Magic is magic.
Magic is undifferentiated. Priest, wizards, shaman and everyone else have access to the same powers, but for different reasons.

4. Magic has to be awesome.
That's all, it just has to be awesome.

If you want to help me out leave a comment. Please help me by doing my work for me... seriously, I will think you're awesome forever.

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