The Nature of Natures
"Nature be understood generically. Here, nature is a set of defining characteristics or qualities, specifically the sum total of characteristics that make something what it is. It is not always possible to agree on a definitive list of these qualities - it is not a simple matter to define the characteristics which constitute 'human nature', for example - but at least we know that a finite list hypothetically exists, and that such a list defines X as a human person, in contrast to Y as, say, a chimpanzee.
"However, nature may also be understood concretely, in at least two ways. Nature may be concrete by definition, as in the enduring Platonic concept of concretely existing forms. Here, nature is not merely abstract, nor only descriptive, for natures exist in actuality in the realm of ideals. But even if one rejects the Platonic ontology, nature may be reckoned concretely in another way: by association or by consequence. If one asserts that natures do not exist in and of themselves, but only as realised in concretely existing things, then there is no abstract 'apple nature', there are only apples, which can be seen to share certain characteristics. On that basis it could follow that referring to a nature necessarily means referring to a specific hypostasis (a concrete thing or person). This logic, when applied to the person of Christ, can become thorny. For if asserting two natures in Christ indeed leads inexorably to positing two hypostases - two concretely existing beings or 'two sons' - we are on untenable ground.