The Confidence Man is the last novel by Herman Melville, and is a statement on culture of the day and on human foibles and gullibility.
The main characters, including the titular Confidence Man, are all weak in their convictions. Almost none of the people he meets during the course of the book are willing to fully defend their beliefs; even the self-assured mystic, Mark Winsome, refuses to engage in a philosophical debate, instead arguing semantics and then passing the Confidence Man off to his disciple, Egbert.
"Pharaoh's poorest brick-maker lies proudlier in his rags than the Emperor of all the Russias in his hollands," oracularly said the stranger; "for death, though in a worm, is majestic; while life, though in a king, is contemptible. So talk not against mummies. It is a part of my mission to teach mankind a due reverence for mummies."
(Melville, The Confidence Man, etext.virginia.edu)
Although he speaks with eloquence, his words are meaningless, since every line is subject to change. Many of the debates are meaningless in nature, and so betray the innate dishonesty of the characters, many of which are confidence men themselves; that is, they are each seeking to defraud others of money, time, and effort, for their own personal gains.
That Melville names few of them is interesting in itself; "The Herb-Doctor," for example, wanders the boat selling patent medicines, but never takes responsibility for their effects (or lack thereof). He has no given name, but instead is only known by his vocation; he vanishes on landing, never to be seen again.
Each character is dishonest in his own way, and each either meets his better or is left to continue, but Melville is merciless in digging out and exposing the failures, weaknesses, and immoralities of each. In fact, the Confidence Man himself does not actually make much money from his efforts; he seems more concerned with breaking down the egos of his fellows than actually profiting from the exchange.