The frustrating part of this debate for me has been (and continues to be) my inability to nail down where my Protestant brethren are coming from both on human nature in general, and on the nature of Christ specifically.
We have agreed that the nature of a thing is quite integral to what it is. If this is true (and most Protestants concede this) then we will always be humans who have a human nature.
The Protestant or Evangelical tends to insist that the human nature is intrinsically and irreversibly evil. An evil thing cannot enter heaven though. Do we lose our humanity when we see the beatific vision? If so, is the resurrection of the body also to be rejected?
In what way does Christ take on our humanity? The Evangelical’s answers to this question seem contradictary. One one hand, they concede that Christ was like a man in that he ate and drank and walked with us. However, they also insist that sin is fundamental to what it means to be human. If this is so, then Jesus Christ is not fully human, being that He did not sin. Either that, or His human nature is a nature unlike our human nature.
Catholic Christology (put forth most spendidly by the Council of Chalcedon) understands Jesus Christ to be a perfect man, the Son of Man, completely innocent and holy in His undefiled human nature. Jesus Christ exists as the Second Adam, taking on a human nature, a human will, and a human soul for all eternity without compromising His deity. The Father wills that all men should be like the Son of Man. Our rebirth involves being regenerated in His image.
As far as I understand, the Evangelical rejects this. Human nature cannot be regenerated from their perspective. It is evil. From this it would seem to follow that being born again involves shedding our humanity. I do not understand this nor do I see the coherence of these beliefs. They appear to be mutually exclusive.