 Why should we accept this sort of account of common natures? Scotus defends it in the context of a rejection of a theory according to which the singularity of a nature requires no explanation other than the nature itself. The theory is in principle capable of development in one of two different directions, and Scotus seems to regard it as a matter of indifference which of these two directions his opponent has in mind. One direction is nominalist: there could be individual natures (of the same kind), and each such nature be of itself particular. The other is extreme realist: there could be indivisible Platonic universals, and each such universal be of itself numerically singular. As Scotus sees it, the only way to explain both instantiability and commonality of kind is to posit the existence of entities (viz. natures) that are divisible. It is the divisibility of the nature that allows its instantiability, and the unity of the nature that explains commonality of kind. Platonism lacks instantiability, and nominalism lacks an explanation for commonality of kind. Scotus makes the crucial claim about natures as follows: