the world that keeps talking after you're gone — "It occurred to him if he…"
It occurred to him if he died everybody would still exist and go home and eat and X their wife and go to sleep.
Context
Solipsism at its plainest and most human: the hall's conversation drifts past the open door, glances in, and carries on uninterrupted, and Gately grasps both halves of the trap at once — that the world will keep talking and eating and sleeping without him, and that he still cannot actually picture that world, because the one consciousness that would have to imagine his own absence is his. The indifferent continuing conversation outside the door is the exact measure of the sealed circuit inside the head.