. Tolkien at one point gave the Nazgul a water-weakness but that apparently went by the wayside - but there may be some residual effect of the idea present in the LOTR. As to daylight, I never saw it as the cause of their problems. It is also implied that they were daunted by fire (Weathertop), but later #1 is described as wielding a flaming sword, plus he didn't seem daunted by the fireworks used in the seige of Minas Tirith either. Tolkien is far from totally consistent in his rendering of the Nazgul. Perhaps it was the light rather than the heat of the brands used at Weathertop which discommoded them?
: The Nazgul could be injured and they could be driven off. I always saw the scene such that the Nazgul were gravely injured by Elrond's "attack" at the ford. Any regular being would have been killed.
I take your point about physical injury, the Nazgul are recorded as fleeing on a number of occasions when pursued by soldiery (rather than sorcery), so their constitutions were not impervious to physical harm. However, physical injury does not result in a being becoming "empty and shapeless." Broken bones and battered flesh still has form. Something other than physical damage was inflicted on the Nine in the flood.
: Gandalf first tells Frodo one of the Nazgul's main problem: they have no mounts. "Their horses must have perished, and without them they are crippled". That is because the Nazgul cannot just steal new horses; they would be too frightened and useless. Thus, the Nazgul were now on "foot"
Yes, but the Nazgul were on foot but they were still close to their quarry. Instead of going after the Ring again, they had to make the long journey back to Mordor (on foot). The mere loss of a horse when so near your goal would not have such a debilitating effect.
: Later Gandalf tells Frodo: "You cannot destroy the Ringwraiths like that...Th power of their master is in them, and they stand or fall by him. We hope that they were all unhorsed and unmasked, and so for a while made less dangerous; but we must find out for certain.
: After finding no sign of them, Gandalf concludes: "...I think we may hope now that the Ringwraiths were scattered, and have been obliged to return as best they could to their Master in Mordor, empty and shapeless, If that is so, it will be some time before they can begin the hunt again..."
Why are they "empty and shapeless?" The physical damage theory does not account for this. If their physical bodies were battered to the point that the Nazgul no longer posed a threat to the Walkers, how were they able to make the arduous journey back to Mordor? Gandalf's comment on their lack of horses implies that he expected the Nazgul to still have physical bodies (if they had become intangible spirits they would not have needed, or be able to use, horses for transport). Therefore, the "shapeless" and "empty" Nazgul still had a physical presence after the flood, and were hale enough to make the long journey back to Mordor; therefore I would maintain that something other than physical injury had rendered them impotent as a result of the flood. Either, the loss of their cloaks (which must have had special properties in this theory) or their dip into running water weakened their powers.
: Thus, it appears that while the Nazgul could be rendered temporarily impotent by regular physical injury, such could not kill them once and for all. This discussion has raised some thoughts in my mind concerning the death of the WK at Pellennor and the general vulnerabilty of the wraiths. Clearly, physical injury could do something to the Nazgul - the physical injury they sustained at the Ford rendered them "unmasked" and "empty and shapeless". But it did not kill them.
For the reasons I have given above I do not think that mere physical injury could have rendered them shapeless.
: I wonder now that the Nazgul were vulnerable to normal attacks, including normal swords. However, the most such normal attacks could do would be to render them empty and shapeless and force them to return to their master. A normal warrior with normal blade could win a fight with a Nazgul (provided his sword didn't dissolve too soon . It's probably best to face a Nazgul with more than one weapon) However, only a special blade ensorcelled with spells for the bane of Mordor or the like could actually kill a Nazgul once and for all. Had Merry not attacked the Witch King with his blade of Westernesse, Eowyn still could have won that fight, but the best result she could have achieved would be the temporary impotence of the WK and not his demise - he would have eventually returned. Merry's strike made him fully vulnerable to death.: Russ
How final the demise of #1 would have been if the One Ring and Sauron had survived is a matter of debate. Sauron and all of the Nine had been rendered incapable of physical existence before, but the passing of a great stretch of time had allowed them to reconsolidate their physical bodies. There is no reason why that may not have happened again. Sauron was cut with a mightier blade than Merry wielded and rose again. Perhaps a Nazgul could only be totally finished off if his own ring, or the One Ring itself were destroyed.
