The process of writing the last post helped me understand Aarnian magic, but it also raised some questions, when I considered some of the logical implications of my rules. One of these questions was: "Why don't wizards explode?"
Despite the amusing mental image, it's a serious question. I try to force Aarn's magic (at the very least, its wizardry magic) to follow the law of conservation of energy. Like solar radiation, the energy that fuels magic bombards Aarn from the Astral Sea. Once a magical spell is prepared in the material world (or so I wanted my rules to state) its energy must be expressed -somehow-, or canceled out by other magic.
So this brought me to the question of why a staff releases its magical energy when broken, but a wizard does not. Obviously, I do like the idea of wizards exploding like staves, but if this were true of Aarn, the entire civilization I've built would have developed differently. Science and knowledge would be mistrusted, and Aarn would be far more like a traditional fantasy setting where wizards are mistrusted and banished from reasonable civilization, with good reason. And that sort of setting is boring and overplayed.
Eventually I decided that because wizards have souls, the spells are attached to those souls and not their physical bodies. Otherwise a wizard's spell would discharge whenever they break an arm or get ripped in half. (Hey, it happens.) But this still raises the question of why a wizard doesn't explode when he dies, and his soul goes through the trauma of death, or when a soul-linked animal dies, with similar results.
What I eventually managed to decide (with some help) was that wizards don't explode because the spell energy follows the soul into the inbetween, and then the astral sea. If a wizard dies, there is indeed an explosion of magical energy, but it takes place in an area where only ghosts and astral channelers will be affected. Perhaps some strange magical effects will persist in an area (such as all the physical objects in a certain radius sharing the ex-wizard's spell resistance) but for the most part, no truly visible effect will happen, while preserving the law of conservation of energy.
Of course, once in one of the nine hells, all bets are off for what happens. For a long while, I wanted wizards to lose their spells when their astral body was destroyed and forced to reform in the afterlife. If they did this, they would either have to explode, or the hells themselves would have to do something with the energy. I'm not so fond of the second solution (I try to avoid deus ex machinas) but I haven't decided quite how to handle it yet. I hadn't thought of making the afterlife so different from Aarn that wizards were outcasts due to their exploding when killed, and I'm still not sure if I like the idea or not. It might explain why the afterlife's technology hasn't progressed beyond Aarn's, though, and then again there's the hilarity of exploding wizards running around everywhere. It's made funnier in a setting where no one can be permanently killed.
As for Aarn itself, I think some justification is needed for why wizards are tolerated in society even if they -don't- explode. A wizard has far more power available to him or her than the average town guard, and it would be far too easy for a wizard to abuse the system and also Aarn's populace.
The simple solution is that wizards are self-policing. The spells in the first 6 tiers of spell levels are more or less as powerful as channeling can get without overchanneling. After that, wizards become exponentially more powerful. A single level 12 spell (the most powerful spellweaves can get) can wipe out a town with one blast. Even without a tenancy to explode, wizards are quite literally walking bombs, if they were to bring all their energy to bare.
In order to help ensure that civilization proceeds without self-destructing, the wizards from taking everything over, or the leaders of communities don't abuse their wizards, wizards themselves have entered into an agreement of mutually assured destruction called the "Wizards Council." The council was probably formed as the result of some long past war of wizards that destroyed civilization. (Again. Probably happened 3000 years ago.) The Council itself is made up of the 40 most powerful wizards alive. Membership is not optional, and there is no way to opt-out. If any wizard gets too big for his or her britches (even a member of the council), the council is there to smack them down and put them in their place.
In practice, the council has not worked as well as in theory. Civilization is still stable, though, so the council must be doing something right. Even if it -is- constantly back-stabbing itself, conspiring against itself, and overlooking the more powerful displays of magic when they occur. The wizard's council has been less about mutually assured destruction, and more about nursing the egos of wizards to keep them under control, while also acting as a public relations department to keep giant displays of magic tolerable by the greater populace.
Wizardry is more or less Aarn's version of nuclear engineering. Like nuclear engineering, wizardy is very dangerous when performed by amateurs, tolerated because it helps to further society, and rarely used to its fullest potential because everyone understands that such a release of energy would be against humankind's collective best interest. The kingdoms and nations of Aarn understand that any level 10 and up spells used in an act of war would effectively destroy whatever goal they had in starting that war, and likely destroy themselves in the process.
The analogy is not perfect however. Nuclear engineers don't confine their experiments to towers for fear of explosions killing pedestrians. There are far fewer nukes on earth than wizards on Aarn. Our nukes are also not self-aware, nor can they decide to set themselves off on a whim.
Wizardry's volatility is perhaps yet another reason for why Aarn's world population is so low. The Wizard's Council, instead of preventing destruction, may simply be used as fodder for the following argument: "Hey, we should tolerate wizards despite all that death and property destruction. Imagine how much worse things would be -without- the Council, and in the meantime, wizardry has given us so many wonderful technological advances."
So naturally, while I love the idea of a wizard spontaneously combusting, if it was commonplace, SWC (spontaneous wizard combustion) would destabilize an already unstable situation. Granted, I can't let such a hilarious idea go to waste, so there will of course be very powerful spells that can cause a wizard to completely discharge all their spell energy. Wizards do still explode occasionally on Aarn. They just don't -always- explode at death.