Greatest Novels Ever
The invisible power that commands the whole cosmos(whom most of us refer to as "God") seems to choose to remain indifferent to our existence, to the sufferings that envelop the world and to the chaos that seems to gnaw within us all. This idea is alluded by Dostoevsky through Jesus' silent response to the inquisitor's harangue. That in spite of all the reasonable arguments presented by the inquisitor, Jesus chooses to remain quiet, not to say a word at all, but at the same time, Jesus' silence also symbolizes forgiveness, acceptance and nonviolence, of utter submission to the Divine Will without complaint, of completely understanding without knowing everything, for it is true that faith begins where reason ends and to be able to understand all, one should be able to forgive all. That's why Alyosha still finds the "poem" very Christian for it holds the very core of Jesus' teaching.
The inquisitor represents Ivan's own views, which merely suggest that he does not believe in a silent God or in a God who abandons His people, which in turn also represent the views of the unbelievers. This I believe is the same predicament most atheists would find themselves. It's a simple form of rebellion, where they defy the Divine's benign indifference but in truth, are also searching to find answers for the eternal truth.