Sounds like Tolkien ("Rivendell") agrees with my 'cynical' estimate of the uses
and limitations of pacifism. Pacifists cannot survive by themselves. They have
a use, but they need protecting.
It also sounds like Tom's "pacifism" in Tolkien's letter is a bit of an
ex-post-facto justification of his function in book, which is after all quite
out of line with the mainstream story as it developed. I doubt many readers
make, or need make, a connection between Tom's refusal to help the quest, and
Frodo's refusal to bear arms while completing the quest.
I did say Tom introduced Frodo to the idea of faith, but that is not the only
place where he learns that particular idea. He may well have heard a good deal
about it from those noted non-pacifists Gandalf, Elrond, and the elves of
Lorien. I also said that Frodo learned from Tom that a higher power helps those
who resist evil of their own accord, as Frodo resisted Old Man Willow and the
Wight before Tom came along.
Frodo, early in his quest, actively resists evil by force of arms and action:
stabbing the wraith, fighting in Moria, fleeing from Boromir. These are not the
actions of a pacifist who believes the powers will somehow help him if he does
nothing. And in so acting, Frodo is just like all the other protagonists in the
book in the fight against evil: weapons must be used, "control" exerted as
Tolkien puts it.
But by the time Frodo casts aside his weapons in Mordor, he does in fact
believe that fighting will do him no good, since his struggle is by then
entirely internal. (Note that Sam does not cast his sword aside, and uses it in
the end one last time to ward off Gollum from Frodo). Has Frodo abandoned a
belief in "control"? No. He is still engaged in the quest, as Bombadil never
was. He has internalized his control, to the struggle of will within him. The
struggle is no longer to keep the Ring from Sauron, but from himself. Later, in
the Shire, I think Frodo, having journeyed to the Heart of Darkness, sees good
and evil in both the Ruffians and the Hobbits, and determines to work to save
the good in both, which cannot be done by the sword, but by example. It is
pacifism at its purest, working in conjunction with the sword to limit the
unnecessary damage done by war.
I think Frodo's pacifism is of a different order than Bombadil's, and reading
Tolkien's words on the issues reinforces my feeling that Pukel-man is right in
his perception of Tom's "theoretical" or "fantastical"
pacifism.

"Wake up and smell the coffee."
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