ladodgers6,
I thought I should mention that "theosis" or "deification" is something rather unique to the soteriological systems of Eastern/Oriental Orthodoxy and Catholicism. Granted the specifics of the term differ -- the prior developing specifically in the context of mysticism and asceticism, while the latter developing specifically in the context of medieval scholasticism. I am no expert in Eastern Orthodoxy, so I will refrain from commenting, but I will give you a quick overview from the perspective of the medieval schools, in the case that you would like a bit more information.
Theosis, as it is used in the east, is a broad term which overlaps two concepts in Catholic thought. The first is
sanctification, as you have noticed, and the second is
supernatural beatitude. Sanctification, as it is used in Catholic thought itself captures two concepts. The first is the
restoration of human nature from the effects of original sin, thus make man just in the sight of God where he was unjust and guilty of eternal punishment. The second is the
elevation of human nature, making man directed to a supernatural end or purpose, namely supernatural beatitude, which is otherwise proper to God alone. Supernatural beatitude involves, of course, the contemplation of God by the blessed, but it is a contemplation of Him which is naturally proper to Himself alone. Consider I Corinthians 13:12: At present I know partially; then I shall know fully,
as I am fully known (NAB). So, the saints see God even as fully as He sees them. But only God can naturally see Himself fully. So it is proportionate to God alone to possess supernatural beatitude. But for the saints to see God as He sees Himself entails that they are supernaturally transformed by some gift to be capable of such a thing, since God has promised such a vision. Such a gift we call supernatural grace, and it makes the recipient like God, because it elevates him to supernatural beatitude. But finally, grace flowers into glory, and it is the vision of God, or supernatural beatitude, which finally makes the saints like Him in a more conclusive way. This is the mysterious, supernatural 'expansion' of human nature to see God. Though the saints are not divine, they become "divinized", in that they participate in God's life. As St. Peter writes:
His divine power has bestowed on us everything that makes for life and devotion, through knowledge of him who called us by his own glory and power. Through these, he has bestowed on us the precious and very great promises, so that through them you may come to share in the divine nature, after escaping from the corruption that is in the world because of evil desire (II Peter 1:3-4, NAB).
Now to make sense of all this.
First is the distinction between what is
natural and what is
supernatural to human nature. That which is natural in this context pertains strictly to the nature of man, considered in itself. Of the natural, we can consider
means and
ends. Natural means are those which can be attained by human nature, at least indirectly. For example, we consider water, food, reproduction, natural virtue, etc. to be natural means. Means, of course, are always directed towards an end in some way. Food and water for nourishment, reproduction for the further propagation of humanity, etc. We could consider these various ends to be
intermediate ends, for even these are done for specific purposes. Eventually (although I will not argue it here), these ends terminate in a
final end, or purpose, of man's life. Natural means, considered strictly by themselves are directed only towards an end for which they are proportionate. Thus, natural means, all things being equal, are directed towards a proportionate natural, final end. The scholastics, along with Aristotle, would call this natural happiness, or natural contemplation, which is looking at God indirectly as supreme Creator and Lord by knowing him through creatures. (For further reading on this, look at Aristotle's
Nicomachean Ethics; Thomas Aquinas,
Summa Theologica, Prima Secunda Partis, Q. 1-5; Austin Fagothey, S.J.,
Right and Reason: Ethics in Theory and Practice.)
However, the scholastics did not think man even in the garden had a natural end, but a supernatural end, because of God's grace.
Of the supernatural, there are two distinctions: the
relatively supernatural, or the preternatural; and the
absolutely supernatural, or the divine. The relatively supernatural refers to that which is created but nevertheless above the nature of man, i.e. angelic. Thus, the scholastics spoke of the preternatural gifts given to Adam and Eve in the garden, namely immortality, infused knowledge, and integrity (immediate subservience of all the faculties to reason, which in our case included the passions), for they are properly natural to angelic nature, not to human nature. Thus they are supernatural, but only relatively so. The absolutely supernatural speaks of what is proper to the divine nature alone, namely, the Trinitarian life, supernatural grace, and the heavenly bliss promised in the Gospel, etc. (For more on this topic, listen to the following
lecture by Dr. Lawrence Feingold -- and this would be the resource to look at if nothing else I recommend. It is a very fine presentation.)
The scholastics thought that, if Adam and Eve had not received sanctifying grace in Eden -- elevating them to be ordered towards an absolutely supernatural end -- they would only have the natural end of contemplation of God through creatures, which Aristotle talks about. This is because they were not due a supernatural end at all; it was disproportionate to their nature; God did not have to give them the grace of supernatural beatitude as their end. But He did, and "lifted" them up, from the very first moment of their creation, from a merely natural end, to a supernatural end. So they received sanctifying grace, which ordered them towards the sight of God as He sees Himself. Of course they lost the means to that end, but they did not lose the
election to the end itself, which they passed along to all of us. So we too are elected to this end, our sorry state notwithstanding. But if that is the case, we not only need to be restoratively justified so as to be absolved of the guilt of original sin, but elevated by sanctifying grace back up on trajectory to this supernatural goal that we were given in Adam, in the beginning. The goal, then, is divinization, or supernatural beatitude, but it does not merely mean justification or even sanctification. It also means being 'expanded' or opened up at our death, when the journey is over, to seeing God as He sees Himself. This 'expansion' or 'opening up' is divinization, or supernatural beatitude. It is in every way a gift beyond what eye has seen, ear has heard, etc.
Divinization or supernatural beatitude, then, is the Gospel as the Catholic Church understands it, and the above is essentially how the medieval Church would have presented it. There is a strongly similar presentation in the Eastern Church, at least on the bottom line. But the consensus is that beatitude is not just an Edenic paradise on steroids; it is something altogether infinitely above that, which is why the news is so good, over and above the mere forgiveness of the penalty of sin.
(For free, online, further reading, see
Catechism of the Catholic Church, nos. 1699-1729;
Man: Called to Share in the Divine Life, lecture series, L. Feingold. For further academic reading, see
The Natural Desire to See God According to St. Thomas and His Interpreters, L. Feingold;
Nature and Grace, M. Scheeben;
Nature and Grace: A New Approach to Thomistic Ressourcement, A. Swafford;
Natura Pura, S. Long;
Beatitude, R. Garrigou-Lagrange)
