What is it, to run away! A mere formality; that’s not the main thing; no, he won’t run away on me by a law of nature, even if he has somewhere to run to. Have you ever seen a moth near a candle? Well, so he’ll keep circling around me, circling around me, as around a candle; freedom will no longer be dear to him, he’ll fall to thinking, get entangled, he’ll tangle himself all up as in a net, he’ll worry himself to death! . . . he’ll keep on making circles around me, narrowing the radius more and more, and—whop! He’ll fly right into my mouth, and I’ll swallow him, sir, and that will be most agreeable, heh, heh, heh!
Porfiry Petrovich speaks these words in Part IV, Chapter V, when Raskolnikov goes to Porfiry’s office with the ostensible purpose of reclaiming his pawned possessions. This quotation gives the reader a sense of Porfiry’s style of speech, energetic to the point of being frantic. It also demonstrates his method of focusing on the psychological aspects of the case, a method that seems to have been Dostoevsky’s as well. Porfiry’s confidence that Raskolnikov “won’t run away on me by a law of nature”—that because he is human, Raskolnikov ultimately will not be able to evade his guilt—provides a sense of inevitability that Raskolnikov will either confess or go mad. Additionally, in Dostoevsky’s writing, every character serves a specific function in the plot; we know that Porfiry’s certainty of Raskolnikov’s guilt will not rest idle for long. This subtle tension contributes to the novel’s suspense throughout.
Finally, Porfiry functions as a mirror for Raskolnikov. His diatribe here seems tinged with the same obsessive, almost mad, tone as Raskolnikov’s monologues. He is the only character whose intelligence is a match for Raskolnikov’s. As such, the magistrate seems at times less like a real person and more like an imaginary conscience, pointing out the moves of Raskolnikov’s mind to Raskolnikov and constantly reminding him that he will be found out eventually.