Quote: How can he see he’s got flies in his eyes if he’s got flies in his eyes?
It reminds me of this (presumably) rather more famous quote from the King James Bible.
Thou hypocrite, first cast out the beam out of thine own eye; and then shalt thou see clearly to cast out the mote out of thy brother’s eye. (Matthew 7:5)
How can you see you have a beam in your own eye (or that there’s a mote in your brother’s) if you’ve got a beam in your own eye?
(That was a rhetorical question!)
What makes the Quote quiver?
Lots of things hook our attention; in this case, it’s the repetition of a whole phrase that requires a double take, and the double take uncovers the puzzle, and the puzzle sets our mind aquiver.
It might be the biblical resonance in the background, but that’s harder to judge.
What is at the core of the Quote?
Rhetorical question (erotesis), paradox, epanalepsis, assonance.
Rhetorical question or erotesis: the Quote comes at the end of an explanation of why a certain Appleby has flies in his eyes.
“How come [Appleby] doesn’t know it?” inquired Yossarian.
“Because he’s got flies in his eyes,” Orr explained with exaggerated patience. “How can he see he’s got flies in his eyes if he’s got flies in his eyes?”
It is a question that implies, not expects, an answer.
Paradox: the implied statement you cannot see flies in your eyes if you have flies in your eyes is self-contradictory at first glance. (And implies that you can never see flies in your own eyes.)
Epanalepsis is the eventual repetition of a phrase. (Strict definitions say it means to repeat the opening phrase at the end.) Repeating the phrase he’s got flies in his eyes helps make the Quote a paradox.
Because of assonance (or actually rhyme) between eyes and flies the Quote rolls off the tongue slightly better than if Heller had talked about planks or motes …