Thomas is certainly very much in line with the patristic tradition and especially with the Chalcedonian theologians — and I’m not sure why anyone would want to follow those who reject Chalcedon, as that would indeed be heretical.

The communication of idioms is the standard, traditional, orthodox manner of interpreting attributions to person and nature in Christ, and this goes back to the earliest days of conciliar, Christological reflection. It holds that anything that can be said of either of the natures of Christ can be said of the person of Christ. But there are attributes of the respective natures of Christ that are not intercommunicable. There are things that can be said of the divine nature that cannot be said of the human nature of Christ, and vice versa. Though everything that can be said of either of the natures can be said of the Person.

So, for instance, it is not said of the human nature that it is deity, or of the divine nature that it dies: though Christ as person is eternal and does die on the Cross. The natures, as Chalcedon says, are united without “division or separation,” true. But they are also united without “confusion or change.”

Leo the Great said in his Tome to Flavian, so foundational for orthodox Christological reflection, that Christ “could die in one nature and not in the other.” The same is true of suffering as applied to Christ. Indeed, the person of Christ suffers. But not the “inviolable” (to use Saint Leo’s term) divine nature. Note: the human nature too is “inviolable,” because it is not blended into the divine nature in Christ’s assumption of humanity.

As for confusing person and nature, it is precisely a rejection of the communication of idioms that leads to confusion of them, in the sense of blending them together conceptually, or of blending the natures together as in a chemical mixture.

Interestingly, Balthasar at least tries to fit his speculations into this orthodox context.

As for phenomenology as applied to Christology, one has to be careful not to fall into the Rahner’s transcendentalist confusions where the analogical distance between finite personhood and the infinite personhood is, at least seemingly, done away with.

And Jean-Luc Marion, though a philosopher and not a theologian, is generally considered orthodox in this regard. But I have not read if he has treated of this subject specifically. I do know that he wrote an essay on Saint Maximus the Confessor many, many years ago, before he was famous. Maximus was, of course, the great defender of Chalcedon who upheld the distinctive powers of the divine and human energies in Christ.

What exactly is “the classical understanding of divine immutability”? Is it the mutability that comes from Greek philosophy or is it the immutability of the God of Israel and the God of Jesus Christ? As for the Thomist claim that “only the humanity of Christ that suffers,” I can only say that this confuses nature and person. Natures do not suffer; only persons suffer. It is Christ who suffers on the cross. The idea that only his humanity suffers seems to say that only his human nature suffers. But this is the reason why Thomas Aquinas is insufficient. Contemporary phenomenology of the body (Chretien and Marion and Levinas for example) should serve as a more adequate vehicle for making philosophical sense about suffering. The problem with Thomists of the “strict observance,” people like Levering and even Weinandy, is that, for them, Thomas Aquinas is not only necessary but sufficient. For them, Thomas IS THE MEASURE OF ORTHODOXY!!! Pace a highly skewed interpretation of Aeterni Patris, the Catholic Tradition cannot be reduced to Thomas Aquinas.

As for your first question, I suspect that it has everything to do with Aeterni Patris. If a pope should have similarly commended Scotus, then the ranks of the Scotists would have swelled, and competing schools of Scotism would have proliferated.

Thomas’s theological approach was commended as standard for the whole Church. Little could the Pope have realized that the embracing of historical methods of textual analysis in the Church, and of diverging views on how to deal with enligtenment rationalism, would lead to “different Thomases.”

Theologians are still burdened by the question of conveying the Gospel in a world scientistically immune to it. Do we ignore science, or deconstruct it? Or, do we embrace it, but try to put it into a wider framework of reason? One’s inclination in answering this question seems to be determinative of how one reads Thomas. Because the theologians in question (from Mercier to Balthasar)do not see Thomas as an historical artefact, but as a living voice who can speak to contemporary humanity, they do not seek simply to repeat what Thomas said but to develop his thinking. This will inevitably bring about different and competing schools.

To be honest, I’d be interested to know if any contemporary theologians are using Scotus’s thought in this fashion. If Scotus is approached in this way, that is, as a theologian who is no mere historical curiosity but whose insights can penetrate the secular mindset, then I suspect his work would also lead to varying interpretations.

As for your second question, there are those who argue that Balthasar locates, finally, “mutability” in the personhood of the Son, or in the interplay of the divine relations, but not in the divine essence. Coherent or not? I’m in no position to decide. That will be a point of debate for the foreseeable future. But it certainly was not a position enunciated by Balthasar in the heretical spirit of naturalizing the divine essence — that is, of making God not to be God. That’s probably more Rahner than Balthasar.

I’ve looked for some comment by Ratzinger on von Speyer without luck. Has he ever addressed the issue in print?