It's not necessarily rhetorical even for actual people in the real world. At least, I often find that when I ask myself questions and answer them out loud (or in writing), I get surprising answers. (Arguing with myself is not uncommon.)
Also, you might enjoy Vinge's Fire Upon the Deep.
"How can I know what I think until I see what I say?"
--E. M. Forster
(Strongly second the Vinge recommendation.)
Every month on the month, Less Wrong has a thread where we post Deep Wisdom from the Masters. I saw that nobody did this yet for December for some reason, so I figured I could do it myself.
* Please post all quotes separately, so that they can be voted up/down separately. (If they are strongly related, reply to your own comments. If strongly ordered, then go ahead and post them together.)
* "Do not quote yourself." --Tiiba
* Do not quote comments/posts on LW/OB. That's like shooting fish in a barrel. :)
* No more than 5 quotes per person per monthly thread, please.