The Magic Mountain
Thomas Mann
Settembrini and humanism against the authority of Naphta, in Chapter VI: Naphta, the Snow, and the Death of Joachim.
Crime and Punishment
Fyodor Mikhailovich Dostoevsky
the theory heard in the tavern (Chapter VI of Part One), the article on ordinary and extraordinary men and Razumikhin's tirade against mechanics (Chapter V of Part Three), the night when he calls himself a louse (Chapter VI of Part Three), the question he puts to Sonia about being a louse or a man (Chapter IV of Part Five), the theory that Svidrigailov treats as just any theory (Chapter V of Part Six) and the dream of the plague of ideas (Chapter II of the Epilogue).
The Brothers Karamazov
Fyodor Mikhailovich Dostoevsky
Ivan's thesis that without immortality everything is permitted (chapter VI of Book II), Rakitin's reduction of it (chapter VII of Book II), the servant's argument about renouncing the faith (chapter VII of Book III), Ivan's Euclidean mind (chapter III of Book V), the refusal in the form of a ticket (chapter IV of Book V), the system of the Inquisitor (chapter V of Book V), Smerdyakov, who charges Ivan with the lesson that without God there is no virtue (chapter VIII of Book XI), the devil who recites back Ivan's article (chapter IX of Book XI), and the lawyer who makes psychology a stick with two ends (chapter X of Book XII, chapter XI of Book XII).
Notes from Underground
Fyodor Mikhailovich Dostoevsky
the stone wall and arithmetic (Part One, ch. III), the first causes that undo revenge (Part One, ch. V), the omitted advantage (Part One, ch. VII), reason that is only reason (Part One, ch. VIII), twice two is four as the beginning of death (Part One, ch. IX), the crystal palace that cannot be defied (Part One, ch. X), the script of revenge taken from books (Part Two, ch. V), the bookish sermon to Liza (Part Two, ch. VII) and the life that everyone prefers by way of books (Part Two, ch. X).