When Ivan read this “document” he was convinced. So then it was his brother, not Smerdyakov. And if not Smerdyakov, then not he, Ivan. This letter at once assumed in his eyes the aspect of a logical proof. There could be no longer the slightest doubt of Mitya’s guilt. The suspicion never occurred to Ivan, by the way, that Mitya might have committed the murder in conjunction with Smerdyakov, and, indeed, such a theory did not fit in with the facts. Ivan was completely reassured. The next morning he only thought of Smerdyakov and his gibes with contempt. A few days later he positively wondered how he could have been so horribly distressed at his suspicions. He resolved to dismiss him with contempt and forget him. So passed a month. He made no further inquiry about Smerdyakov, but twice he happened to hear that he was very ill and out of his mind.
“He’ll end in madness,” the young doctor Varvinsky observed about him, and Ivan remembered this. During the last week of that month Ivan himself began to feel very ill. He went to consult the Moscow doctor who had been sent for by Katerina Ivanovna just before the trial. And just at that time his relations with Katerina Ivanovna became acutely strained. They were like two enemies in love with one another. Katerina Ivanovna’s “returns” to Mitya, that is, her brief but violent revulsions of feeling in his favor, drove Ivan to perfect frenzy. Strange to say, until that last scene described above, when Alyosha came from Mitya to Katerina Ivanovna, Ivan had never once, during that month, heard her express a doubt of Mitya’s guilt, in spite of those “returns” that were so hateful to him. It is remarkable, too, that while he felt that he hated Mitya more and more every day, he realized that it was not on account of Katya’s “returns” that he hated him, but just because he was the murderer of his father . He was conscious of this and fully recognized it to himself.