A specific difference is both indivisible into further species and distinct from all other specific differences

The claim that the explanations for indivisibility and distinction are the same gains some plausibility from an analogy with the distinction between different specific differences in relation to a genus – an analogue that Scotus evidently regards as less controversial, and more familiar to his readers. A specific difference distinguishes two different species of a genus from each other. A specific difference is something indivisible in such a way that is explanatory of a species’s indivisibility