When Zosima returns to his cell, Fyodor is relishing his attacks on Miusov, who flatters himself as an intellectual in the enlightened, European style (meaning not religious).
The conversation turns to Ivan's recent editorial on the ecclesiastical courts, the one that caused such a scandal before he left Moscow to return to his father's home. Ivan argues that the ecclesiastical courts (or the Russian Orthodox Church) should take over the state courts because only they can reform criminals by providing them with a moral guide, something the state courts can't do.
Miusov, who at first considers Ivan an intellectual like himself, agrees with Ivan's argument at this point because he thinks it's almost socialistic: that is, the state disappears as Russia moves toward a utopian society.
But Ivan explains that the state disappears only to be replaced by the Church. (Imagine what it would be like if the United States were governed by a single religious group, rather than a government. Imagine having a church determine your taxes, administer the prisons and the courts, run the DMV, etc. That's essentially what Ivan is proposing.)
Miusov vehemently disagrees with this religious turn in Ivan's argument and accuses him of "Ultramontanism." But Father Paissy is in wholehearted agreement.