This is for anyone who wants to theorize about the mysteries of the Halo story, as cultivated from the game and the series of books. Please feel free to critique my thoughts or share your owm, introducing your own topcs for exploration.
Also, there may be spoilers from the books contained within the following meditations, so consider yourself warned.
Topic #1: Who were the fore runner and what is their deal in all of this?
What do I think? I believe the fore runner were either human or included humans as one of its classes (likely a slave class, I'll explain later.)
Guilty Spark seems to imply this idea. He apparently recognizes humans to the extent that he is confusing them with someone he knows. First, he calls MC "reclaimer." The word of course implies past ownership of something, and now you are claiming it again.
LAter, at the beggining of Two Betrayals when MC is stopped by Cortana from inadvertantly destroying the entire galaxy, Guilty Spark recalls a past conversation with whomever he believes MC to be. It goes something like this.
"Last time you asked me, if it were my choice, would I do it? Having had considerable time to ponder your query, I'd say there is no choice. It has to be done."
He is clearly referencing something that happened before MC ever met him, perhaps from thousands upon thousands of years ago when the rings had to be activated because the flood had become such a threat to the entire universe.
Later in the game, he talks about his fascination with learning about human history, "the document of our lost time together." The reason I think humans may have been a slave class is because he says, "human history, is it?"
Why isn't the time from when GS knew the Reclaimer considered history? If humans had been a slave class, then they would have been denied ownership of anything, even history. They would have been inconsequential, not deserving a record of their existence. Hence, human history begin on earth, away from whatever force had controlled them.
All this of course leads to lots of other questions, but I think I've gone on long enough for right now.