 Building on insights gained through the thirteenth century, Scotus distinguishes two closely related issues in individuation: explaining how a particular is such that it cannot be instantiated (explaining its individuality, its “indivisibility in itself”), and explaining how a particular is such that it is distinct from other particulars (explaining its “division from others”; on this see Park [1988]). The first of these is on the face of it the more complex issue. For various historical reasons, medieval realists tend to suppose that common (shared) natures or essences are somehow divided into their instantiations – as Scotus puts it, divided into “subjective parts.” It is not easy to explain precisely what this divisibility amounts to. Explaining both divisibility and its opposite, Scotus states the problem of individuation as follows: