You are completely correct on the note on standard Surgebinders--that was a gross lapse of logic on my part.
And yes, I was saying that spren were the focus as well as a prerequisite to the magic itself.
So at worst, spren are not the focus, but rather the thing that gives a particular person the power to Surgebind. It's the corollary to the Shaod or genetics. Spren appear to grant the powers in sets of two's. Hey, I guess that standard Surgebinding analysis wasn't completely useless; we could probably agree that, if spren grant Surgebinding ability, they give two Surges at a time.
Then, there would a completely different set of ten focuses, one specific to each Surge. I can live with that kind of a model.
It would seem that the most likely possibility is some sort of Body Focus. It has focus in the term itself, which is a good start. We just don't exactly know what a Body Focus is. Like, "Soul." Other than having a great symmetry to Soulcasting, it's... really unclear how the soul focuses the magic. It isn't clear-cut like Aons, metals, or Commands. However, that could very well be because no one on Roshar has told us what the crap a Body Focus is. There could be some ludicrously easy logic to them which clears up the ambiguities.
As I'm reading that, that seems pretty valid on its own right. I'm making another leap of logic and assuming that there are ten different spren which grant abilities, but if that is true, then that would explain the need for ten distinct orders of Radiants. Having ten distinct methods to access the ten Surges would also make a scholar think, "hey, we need to list them separately, and give them each a fancy glyph, since they aren't the same thing as the Radiants themselves." Roshar is a fairly cosmere-literate place, too, and so maybe they simply called them Body Focuses because they are, in fact, the focuses we are looking for.
So you're right. I'm probably wrong.
Regardless of how I think the spren-focus idea is damaged, I must still say that a focus could be the actual thing that grants you the ability. I'm... kind of tired (I've had four hours of sleep since my graveyard where I posted that last rant), so it'd probably be best for me to go to bed before I make a 3000 word analysis and miss something idiotic.
Thanks for your awesome rebuttal, by the way. That was truly excellent.
EDIT: You don't have to agree that spren give power, but I think that is a theory that makes sense.
Edited by Chaos, 31 July 2011 - 01:38 PM.