Keltham puts the stone on his arm, dissociating from the part of himself that wants to flinch and destroying-by-reflection the fear of just that action itself which is not itself the pain.
He waits until his brain understands that the stone itself is not the pain.
He tries to put himself into the frame of mind of somebody who relates to the coming pain as if that were dignity, as if he were proud of how it cannot touch him, leaving the core of him unchanged.
What's the equivalent for pain of 'I am not my beliefs, I am that which updates them, I am not my plans, I am that which chooses them'? Keltham is not... his pain, he's the thing that is unmoved by it? Negative neural feedback does in fact sort of move people though?? Keltham is not his desire not to be in pain? Keltham sort of thinks he is made out of, among other things, desires like that one?
"Carissa, do you know what the equivalent should be of 'I am not my beliefs, I am that which updates them, I am not my plans, I am that which chooses them' for pain?" (This, the second layer of Impartiality, Keltham speaks in Baseline.)