This is another inadvertent reference by a character to Dr Monygham's disgrace,
like the story of the cavern of banditti in Chapter 3-1 .
Monygham, we shall learn later, gave in to torture and attempted to fool Guzman
Bento, arguably "the greatest blackguard on earth," by blackening
his friends' characters in a false confession. Note that Monygham's next utterance,
following this reminder, is made "grimly."
On a deeper level, as the allegory of cynicism Monygham is on a constant campaign
to blacken the notion of character, insisting that men act from the lowest motives
and that the self "is the last thing a man ought to be sure of."