Keltham is not a Keeper and therefore he is going to do something epistemically questionable and, while not assigning bad probabilities over the branched possibilities, live for a time inside the possible world where that vision definitely hasn't happened yet, until he stops feeling like he's going to throw up, and come to terms with the other branches later.
"I have my obvious theory about what that means and why my god would do that. Both of you come up with your theories before I state mine, then we all state what our theories were before we heard the other person's theories," Keltham says. "Security first."