In a new story, at the end, an alien AI introduces itself as "the one" who initiated all the activities in the story (and provides no specific name). Going forward, how would you refer to such an entity: "The One", "the One" or "the one"?
I think I prefer the first, as it offered the term as its desired reference, making it it's official name. It isn't a one, instead it's name is "The One".
I agree, if he accepts it a name, then it's capitals all the way, but very likely to get shortened by people to T.O.
Sometimes long names get initialized (like FDR, JFK or LBJ) but normally part of the name or the way it sounds gets used instead. We like Ike or Madly for Addli (Stevenson, the other candidate). Why move your mouth twice, once for T and once for O, if you can just say One. No one used JW for John Wayne, although Duke was frequently used. I haven't seen BO for Barak Obama. Obama is short enough to be used instead.
Railroad crossing look out for the cars. How would you spell it without any Rs?
Answer:
(wait for it!)
I. T.
(an oldie but goodie.)
The version I've heard/used is
Joker: Do you know how to spell rhinoceros?
Straight Man: Yes.
Joker: Okay, spell it.
Straight Man: R.H.I....
Joker: Wrong! It is spelled I.T.
I think I prefer the first, as it offered the term as its desired reference, making it it's official name. It isn't a one, instead it's name is "The One".
Just like terms of endearment, if Princess is the character's nickname, it's capitalized. Otherwise it's not. How does the reader know it's a nickname rather than a terms of endearment? The author capitalizes it.
Same with your case. If you want the alien to be known as "The One," capitalize it as such.
I agree with @Ernest Bywater and @Switch Blayde, it should be capitalised in the same way that it is identified as a name.
Also, depending on how widely known the being's nature and existence is propagated, and how different factions might feel about the events, an unusual name like that is a good excuse to use different monikers. People who are fans or diplomats would use the official "The One", most people would probably say "the One" a bit more casually (still a name, but no verbal emphasis), distrusting factions might use "TO" then explain that it stands for "totally overbearing", and so on. While language tends to default to ease of use, that's not the only factor which affects nicknames.
Also, depending on how widely known the being's nature and existence is propagated, and how different factions might feel about the events, an unusual name like that is a good excuse to use different monikers.
In this case, the 'entity known as "The One"' is only introduced at the end of the story as the one who's been pulling strings all along. Thus his identify is a secret to everyone but the main characters in the story ... at least until book 2! 'D
