We can also ask what it means for Christ to have assumed humanity:
WLC Q. 37. How did Christ, being the Son of God, become man?
A. Christ the Son of God became man, by taking to himself a true body, and a reasonable soul, being conceived by the power of the Holy Ghost in the womb of the Virgin Mary, of her substance, and born of her, yet without sin.
Steve Hays once
wrote:
"If we view human nature as an abstract universal, then to be human is to be a concrete particular. By "concrete," I mean existing in space and/or time. Angels exist in time, but not in space. Humans naturally exist in both, although humans can exist in time but not in space (the intermediate state)."
I'm still thinking through whether human nature is an "
abstract" universal, but I agree with Steve that we have concrete souls and bodies.
I once asked a miaphysite:
"...if body and soul are really separable - separated at death, for example - does that not imply enumerability is really and not merely theoretically possible within the composition of "man"?)."
His reply was:
"Regarding your question of body and soul, we say the [particular] human nature is the composite one out of two [particular] natures: body and soul. Before the union [your conception], they are insubsistent and do not exist temporally before your conception. At the moment of union, the particular human is out of these two insubsistent hypostases which only logically and not temporally precede the whole.
Death is the unnatural separation of body and soul, [though they would not be considered really separable, because the final cause of soul and body of men is of their union], and in it, the numerical unity of the whole is severed, and the formerly insubsistent hypostases of body and soul still retain subsistence by the fact of their union, but as wholes in themselves [hypostases] and not parts of a whole human nature. The soul hypostasis is the seat of the person [prosopon], and therefore continues to exercise the intellective and volitive powers available to it, while the body hypostasis is without person. At the resurrection, when the body is united to the soul, the soul hypostasis is united to its body, and communicates its numerical subsistence and personhood to the whole human nature, and therefore no longer subsists in itself, but as part of the whole human hypostasis.
To sum, you that you can say
two hypostases/natures of body and soul before the union en theoria [because the hypostases of body and soul precede the union only logically and not temporally] , one [particular] human nature after the union out of them both,
two post mortem by virtue of their unnatural separation due to their subsistence, and one after the resurrection by virtue of the soul communicating its personhood and numerical subsistence to the whole, and subsisting not in itself, but as part of the whole."
The composition of body-soul miaphysites affirm seems to break down when the subject of death is raised. Here is the Christological dilemma as I see it:
1. If the miaphysite affirms that it
is Christ's body that was placed in the tomb, he has just affirmed two hypostases with respect to Christ - that's Nestorianism (and his "final cause deflection is weak).
2. If he denies (as he seems to) that it
is Christ's body that was placed in the tomb, he has rejected Scripture (e.g. John 19:38-42).
That is, that Jesus' body and reasonable soul were separated from each other does not entail one or the other was separated from the hypostasis of Jesus... unless the means by which one disaffirms two natures is a composition which is undone at death (miaphysitism).
Given Jesus' unique status as the second Adam, I'm not sure if this commits one to affirming the same of everyone other human (given the person-nature distinction I outlined earlier, it could be possible). I don't see any problem either way.