  If Plato construes difference as a structural kind that operates in the way we have discussed (the incompatibility range interpretation), he can handle negative predication without introducing a second meaning of heteron. We need not consider all of Theaetetus’ properties to explain the falsehood of “Theaetetus is flying.” The analysis of negative predication is complex: the item negated in “Simmias is not large” indicates a division of the genus size, and the negation designates something different (non-identical, distinct) from largeness within that genus. In the case of Theaetetus’ imagined flight, we must find that activity different from flying within the relevant incompatibility set, a set apparently consisting of our pair of consonant forms: change/rest. Since Theaetetus is currently sitting (a species of rest), his current rest excludes flying (a species of change). One can explain his not flying by appeal to his sitting.