I don’t see existentialism, but I do see a Schroedinger’s Cat analogy. Before you look at the bite you took (measurement), you have eaten and not eaten a worm. Paradoxical.
But Mod 80 is right, if when you look at the apple you don’t see a remnant of a worm then you most likely did not eat a worm.
SJS- as I’m sure you know, the successive halves do sum to 1.