Detect evil is positive -
kill it.
Ahhhh. The Paladin's Detect Evil & the Thought Police. The "orc baby" problem, indeed.
We all knew what we would read here in the five word topic header, didn't we? It's all variation on a theme as old as the game.
The main quandaries of the Paladin and the "Orc baby" problem classicly present themselves as:
- is the creature inherently evil?
- are all monsters hard-wired to be "evil"?
- even if it is predisposed towards evil, can it be redeemed?
- is evil just a behavior or does it require a true selling of one's soul to outside influences or the unlife beyond the grave to "count", absent a demonstrable crime to match the alingment?
- are humanoids and others deemed to have free will and souls to be treated differently?
- does the detection of evil in the absence of a correspondingly evil act amount to the Thought Police? Does the relevance of that question change with the creature detected?
- does detect evil only work on those few creatures who have actively aligned themselves with an evil external power or greater cause?
These are the main points that constantly resurface in these discussions. There are, of course, others.
I think, on the whole, we as human beings tend to make a differentiation along the evolutionary track when considering any other species, be it real or imagined: those creatures that most resemble humans are given the benefit of the doubt with respect to redemption and a presumption of innocence, while as we move away from the human to the , humanoid and then to the monstrous and the abominations, our granting to the creature those presumptions of free- will, redemption and innocence deteriorates until the thing - of whatever age or cycle of development - just merits death for being what it is.
The same can be said for our sense of revulsion at the general appearance of any creature in the real world. The closer something is to us on the evolutionary tree, the less abhorent it is to us.
Kittens are cute>> a mouse is a pest but *can* be cute (woohoo mammals!)>>snakes are kinda creepy>> spiders are really creepy>>> a slug is just plain **icky** - step on it NOW!
(In the real world, invertebrates have no rights!)
FWIW, I can accept how a mind flayer tadpole is not given the benefit of any doubt and is simply killed not as a dangerous animal - but as a dangerous
monster.
How unique and free-willed monsters are treated in the game world is handled by every group (yes, group - I don't just mean the DM on this point) differently.
The rules don't help us much though when it comes to trolls. In D&D terms; the orc is humanoid, the troll is a giant. The orc is OFTEN Chaotic evil, while the troll
USUALLY is.
The devil is in the details. "Often" suggests a much larger parameter for self governance and free will than "usually". Both fall short of "always".
What is very clear during play is that when a creature is listed as says "always" chaotic evil, it's usually for a good reason. The moral quandary of what to do with such a critter never manifests itself.
YMMV.