Pulcheria asks her son if he knows what "it is like to be utterly alone?"; this question is the recurring motif introduced first by Marmeladov, then picked up by Raskolnikov and applied to Sonya and to himself. The effect of this utterance on Raskolnikov is profound since he has just recovered from the same emotions and the same desperation.
Raskolnikov has the sudden realization that the crime, rather than making him above the ordinary man, imprisons him and isolates him from others, even his mother: "It became suddenly plain and perceptible that he would never again be able to speak freely of anything to anyone."
Raskolnikov's dual personality is emphasized again and again in the chapter. At one moment he renews his objections to Dunya's marriage to Luzhin: "If you marry Luzhin, I cease to look on you as a sister." This is his compassionate, humane side speaking now in which he sees his sister sacrificing herself by entering into an insufferable marriage. Then only a few seconds later, he suddenly reverses: "What am I making such a fuss a for? Marry whom you like." Of course, this particular reversal from compassionate to intellectual is brought about by Dunya's terrible justification of her marriage. "If I ruin anyone, it is only myself. I am not committing a murder." This statement forces Raskolnikov to realize that he committed his murder so as to see if he would be able to stand apart and above other human beings; therefore, he must assume this air of not caring whom Dunya marries.
Ultimately, the question of whether to invite Raskolnikov to the meeting with Luzhin must occur before Dunya has knowledge of the money left to her by Marfa Petrovna so that her risking her marriage with Luzhin does not involve money matters. She proves herself to be a true agent and later worthy of the love of Razumihkin.
