Monygham, of course, is leading towards enlisting Nostromo in Decoud's plan; hence his reminders. To Nostromo, though, as to us, the reminders of Decoud serve to bring to mind his position on the island.

On the deeper level, Decoud's "plan" again refers to skepticism as such. On that level, Monygham's response consists of a kind of allegorical agreement, i.e., "Your condition is not merely the fault of exploitative gentlemen, but of the universal nature of things to end in disillusionment and failure, as skepticism foretells."