I'm be very curious about that book I ordered. I think it will answer some questions we're posting here. Here is a section of a review specifically on Sedley's chapter:
David Sedley contributes a helpful chapter about “Epicurus on Dialectic,” in which he considers several ways in which Epicurus’ well-known rejection of the dialectical method reflects Epicurus’ own ontological commitments. One particularly noteworthy aspect of Sedley’s chapter is his discussion of the so-called ‘Bat Riddle’ that Glaucon mentions in Book V of the Republic (89-105), in which ‘a man who is not a man shoots and does not shoot a bird that is not a bird,’ etc. Sedley argues that this riddling description of the eunuch (who is both a man and not a man) who shoots (and misses) a bat (which both is and is not a bird, as it is a bird relative to its gift of flight but is not a bird insofar as it is viviparous) captures the Epicurean view that being is in all cases relative and aspectual, and hence not truthfully or meaningfully disclosed through the kind of dialectical investigation at play in, for example, Platonic division.