The crime: someone murdered Fyodor Karamozov, the wanton, irritable, and sadistic patriarch.
The punishments: Smerdyakov, the illegitimate son, committed suicide after killing his father. Dmitri, the eldest son, passionate and immoderate like his father, whom the court found guilty of the murder, was condemned to Siberia. Ivan, the second son, who was "enlightened" and rational, struggled with the guilt of convincing his half-brother Smerdyakov that since God didn’t exist, everything, including patricide, was permitted.
Optina Monastery (Photo by Иерей Максим Массалитин)
But as the dying monk Zosima had revealed and Dmitri soon realized, everyone was complicit in and thus implicated for the crime, since, for Dostoevsky, the web of sin entangled young and old to the extend that even children suffered from their peers’ sadism.
Through his dream of the hungry and suffering children, Dmitri realized his guilt in the desire, that mustard seed in his mind, to kill his father and therefore willingly took upon the punishment for the crime he didn’t commit. In doing so, he assumed a Christ-figure, accepting punishment for another’s crime.
The Legend of the Grand Inquisitor revealed Ivan’s enlightened rationalism for a humanistic dystopia, the socialist utopia that Dostoevsky condemned. Only when, in a hallucination, the "devil"--Ivan’s dark side-- revealed the parable of the learned atheist and thus rationalism’s arid futility did Ivan realized his guilt in rationalizing patricide and prodding Smerdyakov to commit it.
And Smerdyakov, who mirrored Ivan’s unconsciousness and who carried the latter’s reasoning to the logical conclusion, like Judas, would not have the chance to repent or atone for his crime. In the end, Dmitri assumed his punishment.
Through the tormented consciousness of Dmitri, Ivan, Smerdyakov and other characters, Dostoevsky grabbled with morality in an enlightened but Godless world, a world that he could not accept.