In Catholic theology, that idea was taken up again by Henri de Lubac and Karl Rahner in the mid-20th century, and has germinated much lesser work since. Fortunately, the idea as most often formulated is, itself, ambiguous in such a way that it can and should be disambiguated into an orthodox and a heterodox version. When that much was pointed out to him, de Lubac dutifully forswore the heterodox version and embraced the orthodox one. But given his philosophical anthropology, so heavily influenced by Heidegger, Rahner could not do the same so readily. It isn't even clear to me that he wished to do so, which is one reason why I've never considered his work in fundamental theology reliable as assigned texts in seminary education. Rahner might be orthodox, but you have to work awfully hard to see how, and he wasn't about to make it easier. For the time being, however, it's easy to disambiguate the idea at issue.
The claim might be
(1) Given that, by eternal decree, God created humanity with the intent of elevating it to a share in his own nature, it is an unalterable fact that that humanity has never existed and never will exist in a state of pure nature apart from grace
or the claim might be
(2) Given what it is to be a created person, i.e. an individual substance of a rational nature, and given the divine goodness, it is logically impossible that God create persons, and thus human persons, without intending to elevate them to a share in his own nature.
My claim, and it is far from being just my claim, is that (1) is orthodox and (2) is heterodox. The reason (2) is heterodox is that it leaves no room whatsoever for the gratuity of grace vis-à-vis nature, and therefore eliminates the very idea of grace as a free gift which God does not owe to us. But (1) does not say that or even imply that. All (1) implies is that, given what God has eternally and freely chosen to do, he has not left himself the option of undoing it. Even though God might not have done it—given what God is and what it is to be human—in fact he has unalterably chosen to offer humanity the free, unmerited gift of becoming partakers in his nature.
Very well: de Lubac's passionate argument for (1) was a much-needed corrective to the medieval and Counter-Reformation theologoumenon of "pure nature." Over time, the idea of pure nature had become an important component of neo-scholastic theology—so much so that, between the two Vatican Councils, most orthodox Catholic theologians were taking it to be indispensable. It was, for example, logically necessary for the widely-accepted theory of limbo, and it seemed to make many points of traditional moral teaching far more persuasive to non-believers, at least potentially, than they would be otherwise. For reasons I won't detain you with, the de Lubacs won the day during Vatican II. Not surprisingly, after the Council the limbo theory withered on the vine and natural-law theory fell out of favor among many Catholic moral theologians. I still think there's a place for both, especially for the latter. But neither now retains the importance in Catholic theology that they once did, and I think that's fine as a needed corrective to the ossified Aristotelianism of post-Tridentine neo-scholasticism.
But people like Photios Jones, of the aforementioned blog, go further. Being Orthodox, of course, Photios cannot be expected to care much about the vagaries of Catholic theological historiography. Perhaps that is why, despite my past protestations, he continues to interpret the Tridentine dogma of original sin as ascribing personal guilt to people who have never done anything morally significant, and to interpret the dogma of the Immaculate Conception as ascribing moral virtue to the Theotokos before she could do anything morally significant. But on the immediate matter at hand, I believe the difficulty to be the same whether one is Catholic or Orthodox. Every responsible theologian has to be able to explain what's gratuitous about "grace" in a sense distinct from what's gratuitous about "nature." Photios doesn't do that and doesn't think he ought to do that. I find that unacceptable.
I think part of the problem is that some theologians, Catholic as well as Orthodox, just don't see what is to be gained by insisting that God's elevation of creation is gratuitous in a sense beyond that in which creation itself is gratuitous. Creation is gratuitous because, not needing anything ad extra for his being or perfection, God nonetheless freely brought forth creatures as an exuberant manifestation and communication of his goodness. That's almost what it means to say that creation was, or more properly is, an act of love on God's part. For some thinkers it's hard to see how God's elevation of rational creatures, angels as well as humans, to a share in his own nature is or even could be gratuitous in a sense beyond that. And in a way they're right: since grace on any responsible account is indeed an "exuberant manifestation and communication" of God himself, we have not distinguished it from creation just on that account. But that is hardly the last word, nor could it be if we are going to preserve the very idea of gratuity in grace at all.
If grace is to be received gratefully as a gift, rather than as payment on a debt God owes us just in virtue of what we are, then what we are, i.e. our nature, has to be capable of a good measure of fulfillment without grace, even though grace brings immeasurably more fufillment. This is not to say that, in the actual world, anybody is going to end up with a "good measure of fulfillment" that is somehow "purely natural" not of grace. That's not how God has set things up. We are all, each of us, called to be "gods" (cf. John 10: 34) who, if we respond to God's call on his terms, will forever enjoy more beatitude than we can possibly imagine while on earth. But the absolutely key point is that it didn't have to be that way. God could have created beings counting as homo sapiens without destining them to become gods and just allowing them all to grow into what a life-loving Aristotelian might think of as the good life. If God had done that, we would not have known what we were missing because we would never have been offered anything more and hence would not have been aware of anything more. Such was the kind of innocent happiness of "pure nature" that Aquinas thought infants in limbo would enjoy. I believe that, if there is such a state at all, it cannot be permanent; infants who have died unbaptized await divinization through the intercession of those who love them. But that is strictly a matter of opinion.
But there's a proposition afoot which is not a matter of opinion. To insist that nature could never have been enough, that not even God could bring about creation without elevation even in principle, is in my view a version of the idea that God must always do the best possible things given what he is and whatever it is he's already done. That idea has a certain philosophical pedigree and appeals to some theologians. But I don't think it's an authentically Christian idea. There is no "best possible world." Given how the world actually is, there isn't even a best possible way it could become. The orthodox doctrine of grace tells us nonetheless that the world, and what it will become, is far better than we deserve.
