[Bonus thanks to BobTheEngineer <3]
Maybe in some ways, Sylas had always known that there was something quite special about his brain. However, the Omnimous never told him directly what it was because it had decided not to. As for Sylas himself, it was hard to truly understand the connections and differentiations between the Will, matters of the soul, and the brain.
The separation wasn't so clear, and it wasn't even clear if there was this so-called "soul" in the first place. Will was, for all intents and purposes, about as much of a soul as one could actively expect it to be.
It acted independently of the body, it was illusory, and it could survive—at least for some—beyond the destruction of the body.
