The irony of Frank's attack
When Frank attacked Morris, he probably didn't intend to come back and beg him for a job, but he does exactly that. Frank's basic moral dilemma is how he should treat Morris, knowing that Morris's clumsy attitude makes him an easy target for theft. Ironically though, Frank seems to admire Morris, and he seems to resent his propensity to do evil.
The irony of Frank's skill in business
One might think that a bottom-feeder like Frank would be naturally bad at business, since business seems so civilized, but actually, Frank's ability to lie and manipulate and to solve problems without the constraints of morality allow him to thrive in business. Morris simply is not as powerful in business because he is essentially good and honorable.
The irony of Morris's clumsy moralism
Morris is the novel's depiction of essentialism and moralism, but the novelist chooses to expose Morris for his weakness and his severe clumsiness. He often waits for people to "do the right thing," instead of making use of his ability to change his environment. This makes him passive and ineffective, and ultimately, it prevents him from being able to enjoy the benefits of his labor.
The irony of Frank raping his own girlfriend
When Frank rapes Helen, there is an instance of dramatic irony. The reader already knows that if Frank would just calm down and listen, he would learn that Helen has decided to have sex with him. Instead, he allows himself to be overtaken by his lustful, evil urges, and he does the worst thing he can possibly do to the one person he claims to love most.
The irony of Frank's conversion to Judaism
At the end of the novel, Frank gets himself circumcised so he can convert to Judaism, which is bizarre, given that he has violated his own girlfriend. He's consistently stolen from the man he depended on most. For him to do the difficult and painful thing of undergoing a religious transformation seems to be out of sync with his typical behavior, and the novelist ends the novel this way, as if to raise a question but not to answer it. The question seems to be to what extent Frank's conversion actually represents a change in his character, or whether he has simply fooled himself into believing that he has changed, using his unique ability to lie. Is he lying to himself, or has he truly changed? The novel ends before the answer can be found.
