An interesting jeu d’esprit at Waggish:
pick a work of literature or philosophy (or poetry, if you can make it work) and a sentence from that work that, if the sentence had been excluded from the work, would have made the greatest difference in the work’s interpretation/reception/history in the following years.
As david feil says in the comments:
It seems that there are several different types of sentences that can be turned up by this question. There are sentences which change the way you read the text, whether it is an explicit instruction (like your Wittgenstein) or a cryptic clue. There are sentences that are so eruptive that they anchor the rest of the text (Conrad’s “The horror, the horror” or Faulkner’s “I don’t hate the South, I don’t hate it” [from Absalom, Absalom—LH]). There are sentences where the text reaches its most crystallized coherence and turns into some sort of poetic easiness. There are sentences which for arbitrary reasons have been given a lot of critical attention (“My mother is a fish.” [from Faulkner's As I Lay Dying—LH]) but despite their immediate impression don’t really define the text as a whole at all. And then there are the sentences which an individual latches on to as their personal lens of the text, but might have nothing to do with the general reaction…
I think we can eliminate the last category as irrelevant to the spirit of the game (and with my irritating editorial nitpickiness I must point out that “I don’t hate the South” is as apocryphal as “Play it again, Sam”; after Shreve asks “Why do you hate the South?” Quentin responds “I dont hate it,” going on to think “I dont hate it … I dont. I dont! I dont hate it! I dont hate it!“—right up there with “yes I said yes I will yes” in the Memorable Endings sweepstakes). In terms of the original formulation of the question, what comes to my mind is “‘The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.’” (Through the Looking Glass, Chap. 6) Interesting thing to consider, no?