First, it exemplifies precisely the case Tolkien wished to advance: Use
of the Ring -- no matter how good the purpose -- would corrupt the user, turn
the user into the Ring's slave.
Second, I think it adds a lot of point to Frodo's
self-sacrifice, if he willingly and deliberately exposes himself, i.e. the
integrity of his personality, to the powers of evil for the saving of the rest
of the world. A witting self-sacrifice is far more moving than an
unwitting one.
Third, I would argue that a Higher Power's ordaining that
Frodo should hold the Ring implies an authorisation to make decisions about if,
when, and to what end to use it. Gandalf, Aragorn, and Galadriel -- all
of whom explicitly reject the Ring -- know they are not authorised to take such
a decision. Boromir's sin is to think that he is so entitled. The
argument that the weapons of the Enemy cannot be used against him applies, I
think, to everyone but Frodo to whom the Higher Power has granted this
right. The danger of using the Ring is that the user will just become as
Sauron. (Note also that Frodo and Sauron will, in the end, share one
horrifying physical characteristic: both will have only nine fingers.
Gandalf's prediction about the the result of the Ring's use is terribly borne
out.) Frodo's right to hold the Ring implies a right to take this chance,
a right to gamble with his own life for the saving of
all.
__________________________________
All that is gold does not glitter,
Not all those who wander are lost;
The old that is strong does not wither,
Deep roots are not reached by the frost.
From the ashes a fire shall be woken,
A light from the shadows shall spring;
Renewed shall be blade that was broken,
The crownless again shall be king.
