Sorry, I know this thread is old, but it's something that came up in one of our games too so here's the explanation.
You musn't confuse mind and soul. The mind is made up of the physio-neurological process of the human (living) body. It is the result of electrical impulses through the nervous system and the generation of chemical substances through the body. The ability to think, imagine as well as consiousness, emotions, these are all part of what is called the mind.
. . . .
A soul is a conceptual entity. It is intangible, and thought to be made of so god-like force or universal energy that fills all living creature. Some might say it comes from some other unseen and ideal world, where souls will return afterwards, while other might think of an invisible paralelle universe made up of some sort of soul energy which surronds and penetrates us!
In real life, a mind is a very real thing, although extremely complicated and far from fully understood. On the other hand, a soul is not as widely recongnize to actually exist; no one as actually seen one (no one you know), it might or might not affects things around or even our physical body, and you can explain the existence of things that live without the necessity for one. It's intangible and conceptual, it's an attempt to explain things we don't understand.
In D&D however, mind and soul or both 2 very real things. Most living creature have both. The mind allowed them to think, act and basically be living creatures; it gives them emotions, make them dream, etc. The soul is the collection of all the character experience, his identity, whether it's built with the current life or comes built-in, and leaves the character at his death.
I was following you for a little while but this seems to get squidgy here when you define souls.
You say you must not confuse minds and souls and these are different real things in D&D. Minds are thoughts and emotions, the ability to think, feel, be conscious, and imagine. Yet you say the soul is experience and identity. These are not part of mind? A collection of experiences is not part of thinking and consciousness? Identity is not part of consciousness? Are choices made by the mind or the soul in a person?
I'm trying to think why you come up with that definition of souls for D&D cosmology.
Some creature like outsiders and elementals are souls given a physical body, and the soul is destroyed when they die (the soul does not 'depart'). Nevertheless, both are an important part of every living creatures.
In the light of all this it's easy to understand undeads' immynity to mind-affecting. While some undead do still have soul (ghost, vampire, lich), the fact that they don't have physiological functions prevent them from having mind. Thus vampire could still be enraged but the absence of physiological function prevent this rage of having any actual effect on his body; he would not generate adrenaline and therefore not gain moral bonuses from rage for example. Or an intelligent undead could be weary of a situation, but is body will not tremble in fear because there will be no chemical generated by is body. They can't be paralysed because the body doesn't actually moves, magic moves it, and the would not be hypnotized because while they see it's definitely not through neural response and is, I guess, attribuable to the unnatural forces at work.
But the mind is not what control the body anymore. The body is animated through some very unnatural phenomenom, usually by magic or some divine intervention.
A soul without a mind lacks what? The ability to think, feel, be conscious, to imagine? Are you saying intelligent undead cannot think, be conscious or imagine?
These are not mindless creatures. That is a separate quality for things like animated dead and most constructs.
If they don't have minds this leaves a gap for what fills these functions that they perform.
Does the animating negative energy provide their consciousness, thoughts, and imagination, their mental ability scores?
You say an elemental is a soul given a body. A non-mindless corporeal undead seems to be the same thing, a soul given a body.
Sure a vampire could talk about love, but he's not feeling it in his body; his soul might be longing for it, for a lost love, but it's just an illusion, or rather, he is 'feeling' it because love is also a concept, something that our mind makes up, and I guess could be remebered by the soul.
Things seem to be getting mushier. Isn't longing an emotion and therefore a mind thing? What does the soul of a vampire have to do with concepts our minds make up if vampires etc. are souls without minds? Are you saying they can only remember emotions and thoughts and consciousness and not actually have them? However thoughts and consciousness seem to be a necessity for a sentient undead and emotions are typical.
Magic that affects the soul can unsually affect intelligent undead (trap the soul for instance), but mind affecting effect will remain useless. The same goes for plant type (no nervous system, no chemical stimulation in the usual human sense), as well as construct and ooze (which are usually mindless on top of that).
I've never had Trap the Soul come up before but do undead have life forces to be affected as per the spell? What difference does it make under the spell description whether you are talking about a vampire with intelligence and a soul or an animated skeleton without either? The target is simply one creature. The effect is to put its life force and material body in a gem.
But to get back to your big point:
So Plants have minds but no nervous system or chemical stimulation in the usual human sense. They have minds but different ones and so are unaffected by mind affecting magics.
Elementals and lantern archons, in contrast, have minds despite being animate material or glowing balls of holy light. Despite having no nervous system or chemical stimulation in the human sense they can be controlled by mind affecting magic that treants can not be.
And undead have no minds (though they can do everything a mind can do) though they are not mindless. And this is because their bodies are dead and they therefore do not feel anything? Their thinking and feeling is not done by their mind but by the unnatural animating force for them.
The only exception I can think of are the Green Star Adept (CAr), who as no physiology and yet is not immune to mind affecting and elementals, who are not immune to mind affecting, but then I guess you can't understand every supernatural things in term of real life explanations.
If there is a creature with a soul but not a mind what does it lose besides the ability to be affected by mind-affecting spells?
