This is a restatement of the passage that occurred at the death of Charles Gould's
father.
Like that one, this is explicitly elevated above Decoud's thoughts to the level
of a narrative truth. The cautiousness of the earlier version (action gives us
a "sense of mastery") has been replaced here by more open pessimism:
action gives us a "sustaining illusion" against a reality in which we
are "helpless." Note the ambiguity in which "an independent existence"
can mean either "an objective outer world" or "a discrete identifiable
self." The verdict of illusion is leveled at both.