RESPONSE: The reader who asked this question followed up with: “if they don’t, can they be hurt by physical means? Can they be harmed by wonderful weapons?”
This is among the all time Great Debate questions. You will never ever find a response that satisfies everybody. But the majority of people appear to agree that these are three various kinds of animals. Let’s look at exactly what we know about each of them:
A Nazgul on a horse in the Shire. Were they guys or ghosts or something else altogether?
A Nazgul on a horse in the Shire. Were they men or ghosts or something else entirely?
The Nazgûl are no longer living men, however they were when living men who– having actually used and used Rings of Power for some unidentified length of time– slowly faded up until they lost most if not all their physical presence. They are like ghosts but not actually ghosts because they did not experience a minute of particular death.
In order to engage with the physical world the Nazgûl required clothes that was, obviously, enspelled (although Gandalf only states to Frodo in Rivendell “the black robes are real bathrobes that they wear to provide shape to their nothingness when they have dealings with the living”). These spells enabled the Nazgûl to move about as if they had physiques, even to smell fragrances that regular, living men (or hobbits) could not smell. Who cast the spells? Tolkien doesn’t say, although the Nazgûl just solution to Sauron so I believe it unlikely anybody aside from Sauron would have offered the Nazgûl their semi-physical shapes.
We understand that this magic might be broken or compromised by the swords of Westernesse that Tom Bombadil recuperated from the wight’s barrow, because Merry’s sword-stroke achieved that much. And yet it required Éowyn’s own stroke, with her (apparently) normal sword to dispatch the Lord of the Nazgûl once and for all.
During her fight with the Lord of the Nazgûl, right after he shattered her shield and broke Éowyn’s arm, his eyes flashed. This is, to my understanding, the only time that anybody not wearing a Ring of Power is said to have actually seen any physical element of among the Nazgûl. Was this his human kind briefly making itself noticeable since of his anger or was it something else, perhaps showing the wicked power he wielded as a servant of Sauron?
Merry’s stroke triggered the Lord of the Nazgûl excellent pain, enough to make him sob out, however the sword was captivated so does that make a difference? Would any regular blade have caused him discomfort? We just understand from exactly what Aragorn said just after the encounter at Weathertop that any blade that struck the Lord of the Nazgûl was damaged. Éowyn’s own sword was ruined when struck the Lord of the Nazgûl a last time, and she and Merry obviously heard him yell as his spirit flew up into the air.
She did not kill the Lord of the Nazgûl but his spirit ran away the battlefield. He lost the form of corporeality for all intents and purposes. But when his spirit passed over Frodo and Sam they both also heard it. A physical guy’s body would not have actually flown up into the air like that. The battleground was strewn with the bodies of the killed. No one else flew up when they were struck by a weapon. So whatever the Lord of the Nazgûl was at the time, he was not a living, biological creature.
When Frodo confronted the Nazgûl at the Ford of Bruinen Tolkien composed that “they appeared to have cast aside their hoods and black cloaks”; hence, when the Rangers and Elrond’s folk searched for indication of the Black Riders after the flood and they discovered only dead horses and a tattered black cape, the cape itself does not represent much. Gandalf concluded “I believe that we might hope now that the Ringwraiths were scattered, and have been required to return as finest they could to their Master in Mordor, empty and shapeless.”
Being “empty and shapeless” is Tolkien’s way of stating they were not physically manifested. Did he imply they were ghosts? That’s the million dollar concern.
The Barrow-wights were spirits sent out by Sauron to inhabit old remains. They are based on animals from real folk tradition. Tolkien does not say exactly what kinds of spirits they were. We just understand that Sauron might not produce spirits as Ilúvatar could, hence they needed to be spirits that came into existence outside of Sauron’s power. Were they lesser Maiar? Were they trapped spirits of Fairies or Guy? Sauron and Morgoth both had the power to record spirits of the recently slain and keep them in Middle-earth.
The Barrow-wights represent a class of servants that may have been significant however unnecessary to the story. In the very first age Sauron was a “master of phantoms” however in the initial sense of the word a phantom was an illusion, not a genuine creature. The wights were not impressions however genuine spirits doing Sauron’s will. We don’t know their numbers or their particular powers however the wight that recorded Frodo and the hobbits was carrying out a ritual when Frodo summoned Bombadil.
The wight’s bony corpse was animated by Sauron’s will or the wight’s will however it was simply a physical remains. For this reason, when Frodo cut off the wight’s hand it truly did separate from the body. Being already dead the remains needs to have felt no discomfort, although Frodo heard a shriek followed by “a snarling noise”; and whatever power it possessed continued to stimulate the severed hand.
The wight was plainly able to interact with the physical world. And though Tolkien doesn’t say whether the blade Frodo grabbed was enchanted, it did shatter when he cut off the wight’s hand.
The horror that the wights instilled in the Dunedain, making it impossible for them to recover Cardolan (according to a note released in The Peoples of Middle-earth), recommends that the Dunedain might not easily beat the wights and that maybe the wights were too strong for the Dunedain to get rid of. Possibly the fairies could have driven out the wights however Tolkien does not address the question why they cannot do so.
I don’t think the spirits of the wights could have been damaged. Nor do I believe they could have enchanted the corpses by themselves. They needed Sauron’s power to animate the dead but they themselves were not living creatures and could not have been killed anymore than the Nazgûl could be.
Some people fast to point out that in early drafts of the story Tolkien intended for the wights and Nazgûl to be of similar kinds, but this kind of thinking ought to be declined. We have no idea that Tolkien meant to retain that connection. Thus, any speculation that the Barrow-wights were lower ringwraiths is wild, unverified inference based upon a lack of denial instead of a declaration of truth by the author.
The Dead Male of Dunharrow are merely ghosts. The book states that after Isildur cursed them they slowly died and started to haunt the hills around the Ered Nimrais. The physical weapons of Sauron’s servants obviously did them no harm when the Dead Guys took the ships at Pelargir. Of course, the narrative suggests that nobody remained to combat them, either. So we’ll never understand if Tolkien felt there were weapons that might hurt them.
In a note about Baldor, Tolkien wrote that he was attacked by living men, guardians of the temple he had actually discovered who followed him into the Courses of the Dead.