Even a physicist might say that magic must come from somewhere. There’s a fine distinction between the origins of magic and its sources.
The origins of magic in our world is the answer to the question, “Where does magic come from?” And the answer can be the universe (nature) or the gods (or a being with god-like abilities). There aren’t many more options, though we can get more specific than the “nature” option, such as saying it’s radiation, or a lifeforce, or some other energy. We don’t need to explain it to an audience. Magic is accepted. Its origins are a philosophical question and therefore ignored if we choose to, whereas the source of a wizard’s power is a practical matter to which we should pay some attention.
To perform magic, a wizard must draw power from a source regardless of the origins of that source’s existence. Inventing sources is an easy way to create multiple types of magic, one per source, if desired. What follows an inexhaustive list of possible sources:
- The planet
- The solar system
- The sun
- The moon(s)
- Ring system (like Saturn)
- Other realities
- Other planes (like the Astral plane)
- Parallel dimensions
- Demons/angels, etc.
- Plants, animals, humanoids, etc.
- Souls (possibly from the living) or “lifeforce”
- The “force” from Star Wars
The latter option is an implied one in many stories, though only Star Wars (italics) calls it that. The energy just exists all around us and those with the talent can sense and manipulate it. A large source, such as the universe, has an advantage. When a wizard draws energy from a source, it seems reasonable that the source is temporarily drained. An analogy would be blood drawn from us. It replenishes in time, but of course someone can take it all, killing us. A truly powerful source like the sun or the universe is unlikely to be noticeably drained.
But if magic draws energy from living beings, it seems clear we could kill them by taking too much at once, or too often. Wizards could draw from multiple sources to mitigate this. We should determine the source of our magic and within what radius from the wizard that source must be. This is irrelevant with some sources that permeate everything or are seemingly always the same distance; while a planet gets farther or nearer to the sun, this is imperceptible to the naked eye, but what if wizards are always weaker in winter because their source, the sun, is dimmer? But then perhaps it doesn’t matter that the radiation and other elements the sun expels in our direction change distance. It’s up to us to decide. But we’re always looking for ways to limit what sorcerers can do and this is one way.
If a wizard draws from the living, it’s an obvious way to kill people, intentionally or not. But perhaps only some species can be so drained. Either way, imagine this person leaving a trail of corpses or people who’ve suddenly got a type of “sickness” with symptoms indicating a wizard used them as a source, likely in violation of the law. Consequences make for conflict, which makes for story. If we don’t have a need of this source being impacted, then we can decide the source is everywhere, in which case, we can also avoid mentioning it at all.