Fauchard1520
Adventurer
At some point, you need to draw a line between Good and good, or Evil and evil. Dungeons & Dragons assumes a cosmology where the concepts of Good and Evil are primal forces that permeate reality, and certain magic stains your soul. If you cast too many Evil spells, then you become Evil for the purposes of magic, regardless of whether you do good or evil things.
One of the very first characters, in one of the very first D&D games that I played in, was an Evil necromancer who used the undead to perform manual labor and to take the place of living soldiers on the battlefield. If someone needs to suffer, then it might as well be the mindless undead who can't feel anything, right? The necromancer was definitely a good and noble person, even though he was considered Evil for the purposes of magic.
I think that the way it's supposed to work is that the stain on your soul should influence your behavior. Even if you have good intentions, summoning a bunch of undead will make you magically Evil, which will then make you more inclined to perform evil acts. Or if you're a good person, who commits the evil act of summoning a Good creature to suffer on your behalf, then the magical stain of Good (from casting a Good spell) will counteract the non-magical creep toward becoming evil (from committing evil acts). I think.
So in the case of my evil summoner who kept summoning Good creatures to watch them die, repeated castings of that Good summoning spell should have eventually corrupted her over toward not being evil anymore. (At which point she would stop casting that spell, because it no longer seems like a fun thing to do.)
Awesome summary, Saelorn! That is indeed where I'm coming from. I've got to wonder though: Does the intent of watching good things suffer counteract the Good influence of the spell? In other words, is using that kind of magic explicitly for evil acts enough to counteract the Good act? Because if so, your long-ago noble necromancer was A-OK.