| Quote #1
"Besides, I can't bear it that some man, even with a lofty heart and the highest mind, should start from the ideal of the Madonna and end with the ideal of Sodom [...] No, man is broad, even too broad." (3.4.29)
In a typical moment of muddled but surprising eloquence, Dmitri articulates one of the main points of the novel: without spiritual guidance, man's tremendous imagination can't differentiate between good ("the ideal of the Madonna") and evil ("the ideal of Sodom").
| Quote #2
[Alyosha's] mind, too, was splintered and scattered, as it were, while he himself felt at the same time that he was afraid to bring the scattered together and draw a general idea from all the tormenting contradictions he had lived through that day. (3.10.1)
Here Dostoevsky paints a particularly sophisticated portrait of what happens when we think. Without an "idea" to make sense of everything that happened, Alyosha can't organize his thoughts: all he has is a muddle.
| Quote #3
"For those who renounce Christianity and rebel against it are in their essence of the same image of the same Christ, and such they remain, for until now neither their wisdom nor the ardor of their hearts has been able to create another, higher image of man and his dignity than the image shown of old by Christ. And whatever their attempts, the results have been only monstrosities [...]" (4.1.54)
The skeptic, despite his rejection of Christianity, still needs an idea. This thirst for an idea is inescapably human according to Dostoevsky; you can't argue it away. But without the divine imprint, any idea that the skeptic comes up with necessarily falls short in a grotesque way.