AtD translation: atonement

[Mike Jing]

P688.7-14   The first step in our Discipline here is learning how to
re-acquire that rarefaction, that condition of light, to become once more
able to pass where we will, through lantern-horn, through window-glass,
eventually, though we risk being divided in two, through Iceland spar,
which is an expression in crystal form of Earth’s velocity as it rushes
through the Æther, altering dimensions, and creating double refraction. . .
.” He paused at the door. “Atonement, in any case, comes much later in the
journey. Do have something to eat, there’s a good chap.”

In what sense is "atonement" used here?