DanielCC wrote:

I want offer what I hope is a respectful criticism of orthodox Christian protology and some of the consequences that follow from it. I'm sure over the millennia Catholics will have an answer to these and admit that may grasp of the dogmatic theological issues may not be the strongest; none-the-less here it is.
 
I refer to the idea that Man has no innate capacity for union with God, for the Beatific Vision to use Catholic terms or Theosis to speak in the language of the East. If God created humanity with the purpose of their participating in the fullness of His being and becoming themselves thus divine why on earth shouldn't that capacity be of their essence? Why have it as something super-added later, as if it were an after-thought, through Grace?

First, neither for angels nor for men was the participation of divine nature/theosis super-added "later" in a temporal sense, as both angels and men were constituted in a state of theosis from the very moment of their creation. This is taught explicitely in the Catechism:

375 The Church, interpreting the symbolism of biblical language in an authentic way, in the light of the New Testament and Tradition, teaches that our first parents, Adam and Eve, were constituted in an original "state of holiness and justice".250 This grace of original holiness was "to share in. . .divine life".251

Secondly, grace/theosis is not the same as "Beatific Vision", but the latter is the full realization of the former. Neither angels nor, obviously, men were enjoying the Beatific Vision immediately after the moment of their creation.

Now we can restate the question correctly as:

why on earth shouldn't that participation of divine nature be of their essence? Why have it as something super-added to their essence, as if it were an after-thought, through Grace?

There are probably a number of sources from where to answer it according to Catholic orthodoxy. I will choose one I have in mind, from Prof. Bryan Cross of the "Called to Communion" apologetics site. Quoting from his article at

http://www.calledtocommunion.com/2011/06/michael-horton-on-terrence-malicks-tree-of-life/

"The fact that the creature is not by nature proportionate to seeing the inner Life of God is not a “flaw” or “imperfection” in the creature; it is a necessary result of the Creator-creature distinction. Creatures are finite; God is infinite. God alone has the beatific vision by His nature; man does not have the beatific vision by his [i.e. man’s] nature. And that is why man can attain the beatific vision only by a gratuitous divine gift in addition to our nature. In order for creatures to enter into the divine Life of the Holy Trinity, those creatures must be elevated by being made partakers of the divine nature (2 Peter 1:4). To deny that is either to reduce the divine nature to the level of creatures, or to elevate man’s nature to the very nature of God, and thus deny the Creator-creature distinction."

DanielCC wrote:

To drive this point home further, even if we grant that God created Man without this capacity with the intention of gifting it to them later in some fashion (some of the Scholastics held Christ would have still became incarnate had Adam not sinned) why then place the first man and woman in an unnatural state?

Three confusions!

1. The "capacity" for grace/theosis is natural (called "obediential potency"). It is theosis which is not natural, which does not mean that it is "unnatural", i.e. against nature, but "supernatural", as explained below in point 3 and the subsequent quote.

2. As I said before, God did not have "the intention of gifting it (theosis) to them later in some fashion", but gifted it to angels and men at the very moment of their creation.

3. The first man and woman were not placed "in an unnatural state", whether you refer to theosis or to the preternatural gifts. Theosis in particular fulfills in a most excellent way the desires and tendencies in rational nature, both angelic and human, (*) which does not mean that a rational nature would remain forever frustrated if not granted theosis, which was the error of de Lubac. The preternatural gifts, in turn, strengthen nature and therefore are not "unnatural" either.

(*) Quoting again from Prof. Cross' article:

"To be elevated by grace is not [necessarily] to go from not good, to good; it can be (as it was when God bestowed grace on Adam and Eve and all the angels, prior to any sin) an infinite elevation from a natural finite good, to a participation by that creature in the divine nature which is infinite Goodness. But that elevation does not destroy man, or make him something other than what God made him to be. Grace does not distort, negate, corrupt or obliterate nature. Grace elevates nature while preserving nature,"

DanielCC wrote:

Finally the notion that our realisation of ourselves within this world or within another is in principle never enough to bring us to God leads to the further unfortunate tension, that is between the naturalness and unnaturalness of death. It is not with the eyes of the flesh that Man sees God but with the eye of the soul. If the ultimate end of Man is to be one with God and participate in the Divine Love then the existence or non-existence of the body is irrelevant to that end. The desire to maintain a de facto evil of death is to defend the doctrine of the Resurrection of the Body.  Death is not the 'last enemy' but the door through which we enter eternity; it is bad only in as much it curtails our further realising ourselves in this world.

 
The human soul has not been designed to operate apart from a physical body. The state of separation of soul and body is the exception, not the rule. At this very moment, both Jesus and Mary see God with the physical glorified eyes of their physical glorified bodies, while the rest of the Saints see God with the "eyes" of their souls. But it is the state of the rest of the Saints which is a temporary exception to the rule, not the state of Jesus and Mary. The rule is that the human soul should not exist isolated but informing a physical body.

Thus, the issue of "the existence or non-existence of the body" is not irrelevant, but central to the essence of man as opposed to that of an angel:

Man = spiritual soul informing a physical body.
Angel = pure spirit.

The point regarding death is that, if man had not sinned, after the course of our earthly life was completed, we would have received the glorification of our bodies without experiencing death, i.e. the separation of soul and body.