Given Ralph's hatred of Smike and Nicholas both, it is deeply ironic that Smike ends up being Ralph's biological child. This use of irony may appear quite surface-level to readers—a mere plot device, intended to provide intrigue and keep readers hooked as the story progresses. Given Dickens's social-scientific context at the time of Nicholas Nickleby's publication, however, the implications of this plot point run deeper.
Ralph and Smike are two remarkably different people. Smike is kind, trustworthy, and loyal, looking up to Nicholas as a friend and guiding figure. Ralph is horrible, cruel, and vindictive, intent only on completing those tasks that satisfy his own ends. This difference between parent and child flies directly in the face of Social Darwinism, a philosophy that arose over the course of the mid-19th century. Many Social Darwinists held that personality traits (vices included) could be passed from parent to child, and that if children turned out to be alcoholics, or sexual "deviants," or criminals, the parents were to blame for "passing" those traits down to their offspring. Nicholas Nickleby breaks from this philosophy, showing that Smike "inherits" nothing of his father's moral bankruptcy, choosing to be a good person despite his environment and parentage.
In the following excerpt from Chapter 2, Dickens recounts the history of the relationship between Ralph and Newman Noggs. Theirs is an alliance of exploitation: Ralph takes advantage of Newman, who has few options other than to work for the older man for insufficient pay. Dickens's narrator uses verbal irony to comment on this relationship:
The kind-hearted gentleman omitted to add that Newman Noggs, being utterly destitute, served him for rather less than the usual wages of a boy of thirteen.
The "kind-hearted gentleman" referenced is Ralph, whom in the preceding paragraphs had been discussing Newman Noggs's unfortunate life circumstances with Mr. Bonney. Ralph situates himself as Newman's savior, but neglects to mention that he actually exploited and overworked the vulnerable young man. Dickens's "kind-hearted" epithet is intended as ironic—readers are well aware that Ralph is far from kind.
Dickens may also use this ironic epithet to describe Ralph because Ralph views himself as kind-hearted, or at the very least magnanimous, for taking Newman Noggs under his wing. Ralph "omit[s] to add" that Newman's employment occurred under duress and that Ralph is taking advantage of the young boy. Ralph may neglect to include this aspect of the story because he does not possess the ability to criticize his own behavior, nor hold himself accountable to it.
In Chapter 8, Nicholas has the "pleasure" of meeting and speaking with Mr. and Mrs. Squeers, the couple who operates Dotheboys Hall. Both Mr. and Mrs. Squeers are remarkably out of touch, thinking highly of themselves and praising one another's character. Such praise could not be less merited. The Squeerses are wicked human beings who abuse orphaned children with impunity. The couple's lack of clarity about their immoral behavior produces several ironic moments, including the following example of verbal irony:
[...] Smike received another box on the ear for presuming to contradict his mistress, together with a promise of a sound thrashing if he were not more respectful in future; so that he took nothing very advantageous by his motion.
[...]
‘I don’t know her equal,’ said Squeers; ‘I do not know her equal.
That woman, Nickleby, is always the same – always the same bustling, lively, active, saving creetur that you see her now.’
Mrs. Squeers has many unsavory characteristics that her husband either ignores or does not consider unsavory. Either way, when Mr. Squeers states to Nicholas that he "don't know [Mrs. Squeers's] equal" immediately after she does deliberate, unprovoked physical harm to Smike, Mr. Squeers's words contradict the reality of Mrs. Squeers's character.
In Chapter 54, Ralph and Arthur discuss Nicholas's visit the previous night, during which Nicholas attempted to persuade Arthur not to marry Madeline. Neither man is aware that Nicholas is the person they are discussing; the reader, however, does know—making the following passage an important instance of dramatic irony in the novel:
'[...] You said he was handsome, didn’t you?’
‘No!’ snarled Arthur Gride.
‘Oh!’ rejoined Ralph, ‘I thought you did. Well, handsome or not handsome, to this old man there comes a young fellow who casts all manner of fierce defiances in his teeth – gums I should rather say – and tells him in plain terms that his mistress hates him. What does he do that for? Philanthropy’s sake?’
Within this instance of dramatic irony sits an important kernel of information about Ralph's character. Though he has no knowledge of the person Arthur speaks about, unaware the person is Nicholas, Ralph still sees fit to question philanthropic motives. He doubts any morally upright sentiment, constantly questioning the motives of others because his own are corrupted. The stranger Arthur describes could not possibly be acting simply out of interest in Madeline's well-being, because Ralph could not fathom doing that himself. He is a fundamentally selfish person, and this outlook impacts his initial assumptions about others.