Porfiry begins rattling on about these poisoned cigarettes, and Raskolnikov wonders if Porfiry is going to play the same old game again. He throws Raskolnikov off guard by apologizing for their last meeting — "it was such a strange scene" — and perhaps he acted unfairly. He wants to convince Raskolnikov that he is sincerely attracted to him, and he believes that Raskolnikov is "a most honorable man with elements of greatness in him." Furthermore, he possesses a noble soul and elements of magnanimity.
Porfiry also wants to explain all the various circumstances that led him to think Raskolnikov is the murderer — the pledges, the theory, the illness, the return to the scene of the crime, and other matters. He then explains why Nikolay the painter confessed to the murder. The painter happens to belong to an old religious order, which believes that man should suffer and to suffer at the hands of authorities is the best type of suffering, but above all "simply suffering is necessary."
At the end of his narration, Porfiry then explains how Nikolay could not have committed the murder. Instead, after describing the events surrounding the murder, he announces, "you Rodion Romanovitch, you are the murderer." After making this accusation, Porfiry tells him that he will not arrest him for several days because he wants Raskolnikov to come of his own volition and openly make the confession. To arrest him "is not to my interest."
Porfiry then tells Raskolnikov why he likes him and advises Raskolnikov to learn to love life, not to scorn the possibility of a mitigation of sentence. Likewise, he advises Raskolnikov to suffer "because suffering is a great thing." Before he leaves, Porfiry announces that he has no fear Raskolnikov might be tempted to run away; therefore, he is quite safe in letting him remain free until he confesses.
First, even though Porfiry is able to explain so much, the reader must step back and acknowledge that the information that Rodion Romanovitch is the murderer is still only circumstantial evidence and in modern courts would be insufficient to bring about a conviction.
Porfiry's explanation of the crime and his refusal to arrest Raskolnikov show that he does sincerely like Raskolnikov, but more importantly he also believes in Raskolnikov's greatness. Porfiry's true purpose and mission becomes clear in this chapter. First, one must understand that Porfiry, like Dostoevsky, was a dedicated Slavophil, one who believes that the Slavic people are a type of "chosen people." In other words, Porfiry believed so strongly in the greatness of Russia that he is constantly searching and helping those who he thinks will be the future leaders of Russia or who will be able to contribute to Russia's greatness in other ways. Therefore, he views Raskolnikov as a man of noble character, one of the young intellects of Russia who could be of great service to the state if he learns to reject his radical ideas. Porfiry attempts to force Raskolnikov to acknowledge that his theory is wrong, and from this confession to go on and face life and become one of the most important minds of Russia. If Porfiry were to arrest Raskolnikov immediately, it would ruin Raskolnikov's intellectual redemption through self-realization. But if Porfiry gives Raskolnikov enough time to confess on his own (and thus realize and acknowledge to himself his own error), then Raskolnikov will achieve a greatness in his own right. Therefore, it would be no advantage to arrest Raskolnikov unless it is for simple punishment, and Porfiry has greater things in mind for Raskolnikov than punishment; he wants redemption and greatness from Rodya.
Raskolnikov's confession earlier to Sonya represents one aspect of his character and Sonya is trying to redeem Raskolnikov by asking him to take up his cross and suffer. As a parallel, Porfiry also emphasizes the importance of suffering, which accounts for Nikolay's confession, but Porfiry emphasizes the importance of suffering as a means of expiation, "for suffering, Rodion Romanovitch, is a great thing."