Here are some of my suggestions:
- Emotions: Various emotions can be the source of magic. Love could perhaps be the source of healing magic or enchanting magic, sorrow of necromantic magic, anger of destructive magic, etc.
- Willpower: Magic is the result of self control and force of will. This explanation is most appropriate of psionics.
- Elements: Each element is the source of a particulat type of magic.
- Patrons: Higher beings with inherent magic grant their followers magic and magical abilities. This is the most appropriate system for divine magic.
- Nature: Living things are the source of magic. This has several variants, for example one's own body could act as the source, or the living things all around could do so.
- Souls: Souls of the deceased (or other souls) could be the power behind magic. So could spirits.
- Concepts: Mental concepts could have a power of their own and act as a source of magic. Imagination, logic and reason also fall under this category.
- Belief: Simple beliefs or convictions could power magic. Principles such as "good", "evil", "law", "chaos" and others also fall into this category, which tends to overlap with the 'Concepts' category.
- Physical: Magic is the equivalent of modern science and there are firm physical laws governing its behaviour. It is totally predictable and is merely an extension of ordinary physical world.
I am looking forward to hearing more suggestions.
