Eberhard Jüngel is a Lutheran theologian and Tübingen professor who is author of a book on the doctrine of justification, Justification: The Heart of the Christian Faith. I've been writing about The Legacy of Hans Küng's Doctrine of Justification (JDDJ) and asking how to respond to Kung's question: "Is it not time to stop arguing about imaginary differences? regarding what Martin Luther called the articulus stantis et cadentis ecclesiae ("article on which the church stands or falls"), which is the doctrine of justification by faith alone.
I put this question to expert theologians to learn their response to Kung's question, and asked them in particular what is their assessment of Hans Küng's Justification: The Doctrine of Karl Barth and a Catholic Reflection and the Joint Declaration on the Doctrine of Justification. Surprisingly. Everyone referred me to read Eberhard Jüngel's Justification. The book is accessible and an excellent work on the doctrine of justification that I recommend overall, however I'm most interested in Jüngel's particular views on Küng and the JDDJ.
I've assembled the following quotations from Jüngel's Justification that exhibit Jüngel's opinions on Küng and the Joint Declaration as an answer to Küng's question.
In this first quotation from Jüngel's Justification, Hans Küng's Justification is introduced and briefly assessed positively with acknowledgement that Küng's solution has been approved by many respected theologians and church officials.
In the light of all this, there would seem to be an unbridgeable gulf between the views of the Reformers and the Roman Catholic Church about our ability to contribute to our justification. Nevertheless, according to a number of notable theologians in recent times, this is not an accurate impression. Since Hans Küng's  attempt to demonstrate the basic compatibility of the Tridentine doctrine of justification and that of the Protestants -- mainly represented by Karl Barth -- there has been a succession of attempts to reach agreement on the matter. Among these are the official efforts at rapprochement between the German state churches. Not least of these was the revisiting of the mutual condemnations of the sixteenth century, which took place after a visit to Germany by Pope John Paul II. This was undertaken by the 'Joint Ecumenical Commission', which claimed to have solved the question of the doctrine of justification (among other matters), as follows: 'the condemnations uttered at that earlier time . . . are still important as salutary warnings'.  The Commission continues by saying that they, however, 'no longer apply to our partner today in any sense that could divide the churches.'  There was a strong protest from Protestants about this. For example, Jörg Baur rejected as 'unfounded' the claim that the mutual condemnations of the sixteenth century about justification could not divide the churches of today. In his polemical essay he even described the procedures of the Commission as 'spiritual poison'  as they apparently altered the meaning of the old texts and thus misguided the consciences of people.
Footnotes: [^67] Hans Küng, Justification: The Doctrine of Karl Barth and a Catholic Reflection, trans. T. Collins, E. E. Tolk and D. Grandskou, London: Burns & Oats, 1964 [^68] K. Lehmann and W. Pannenberg, eds, The Condemnatiosn of the Reformation Era: Do They Still Divide?, vol. 1, trans. M. Kohl, Minneapolis: Fortress Press, 1990, 27. [^69] Ibid., 68 [^70] J. Baur, Einig in Sachen Rechtfertigung? Zur Prüfung des Rechtfertingungkapitels der Studie des Ökumenischen Arbeitskreises evangelischer und katholischer Theologen: 'Lehrverurteilungen -- kirchentrennend?', Tübingen: Mohr Siebeck, 1989, 109. [^71] Ibid., 42
Jüngel, Eberhard. Justification the Heart of the Christian Faith : A Theological Study with an Ecumenical Purpose. London: T & T Clark, 2006. 177. Print.
Despite the ecumenical optimism, Jüngel's following paragraph exhibits a personal skepticism of Küng's program. Although he does not deny that Küng's Justification may be correct, he certainly does not affirm it either.
I, myself, cannot always agree with the way the Ecumenical Working Group has interpreted the statements from the sixteenth century. There are times when the seriousness of the controversy as it was in those times is undermined. Present-day Roman Catholic doctrine should not be superimposed on what obtained during the controversies of the sixteenth century. Nor should Protestant theology itself be misconstrued as simply repeating the Reformers' statements of those days. It could simply be that the disputes of that age have become obsolete today because we hear and understand the gospel of justification from quite different positions -- perhaps even without taking up the confessional positions of yesterday. It could be that better insights into the biblical texts free us from the clashes of the past so that certain statements from earlier times appear today as inadequate definitions of the truth of the gospel.
If Jüngel's response to Küng's Justification was waivering Maybe?, his response to the Joint Declaration on the Doctrine of Justification (JDDJ) was a firm No! Jüngel expressed his disapproval of the JDDJ with clarity in this follow quote:
Thus the Formula of Concord rejected the Tridentine idea that 'our works either entirely or in part sustain and preserve either the righteousness of faith that we have received or even faith itself' BC, 557. The Strasbourg Institute for Ecumenical Research tried to blunted this statement by means of an unbelievable series of contortions [. . .] But what do we read in Canon 24 of the Tridentine decree? 'If anyone shall say that the justice obtained, but not the cause of its increase, anathema sit [. . .] I mention this embarrassing situation because it is typical of the defense of the Tridentine position by Lutheran theologians in the interest of ecumenism. There is nothing wrong with a Protestant attempt to understand the Tridentine decree on justification better than it understood itself! But we must do it honestly. We must defend what is there. The Joint Declaration reiterates basically the only part of the Catholic doctrine of justification that was condemned by the Lutheran Confessions, saying that it is still Catholic teaching. And then it goes on to assert that the condemnation in the Lutheran Confessions no longer applies to the Roman Catholic doctrine of justification as expounded in The Joint Declaration. This is one of the scandals in the history of theology of which that Declaration will go on to serve as an example. To accept this amounts to a sacrifice of the intellect on the part of any theologian. But enough of these shameful attempts to excuse ecumenism from due intellectual honesty! What concerns us here is to expound the doctrine of justification positively.
In Jüngel's opinion, Küng's solution indicated that Protestants and Roman Catholics were mutually talking past each other and that the ancient anathemas were no longer relevant today, however the JDDJ was a one-sided compromise by the Lutheran signers and the Vatican signers still affirmed the ancient anathemas as still in place today. (Even Küng admitted that the JDDJ was not without controversy and lamented that his contributions were not recognized.) Again in the following quotation, careful readers will notice that the translator has pointed out a potential intentional translation error by Jüngel:
We may leave open the question whether the Tridentine condemnations of Luther's idea is at all correct. The fact remains that the formula simul iustus et peccator is still unacceptable to the Roman Catholic Church today. In its statement on The Joint Declaration on the Doctrine of Justification, the Catholic Church again pronounced Luther's formula (which is interpreted positively in the Joint Declaration) to be unacceptable to Catholics. It expressly disavowed the facts which this formula expresses. It even located the major difficulty 'preventing an affirmation of total consensus between the parties on the theme of Justification'. This is without any doubt to be found in 'the formula "at the same time righteous and sinner"' which is "for Catholics . . . not acceptable"' . Is the formula really so important that it divides the churches? What does it mean?
Footnotes: [^151] Response of the Church to the Joint Declaration of the Catholic Church and the Lutheran World Federation on the Doctrine of Justification, Clarification 1. [Jungel makes the 'major difficulty' a singular, whereas both the German and the English forms of the document have 'major difficulties' ('die grobten Schwierigkeiten') being found in Paragraph 4.4 'The Justified as Sinner (Tr).] Cf. E. Jungel, 'Amica Exegesis einer romischen Note', ZTh 10 (1998).
An additional important point is that the Joint Declaration on the Doctrine of Justification (JDDJ) is a Lutheran and Catholic agreement, and it addresses specific Lutheran dogmas and symbolic statements that are different than other Protestant parties concerns. A specific example would be how the Augsburg Confession should be understood. In this quote by Jüngel, he expresses his chagrin that the formula 'by faith alone' is absent from the JDDJ:
In the Joint Declaration, the Lutherans decided not to specifically include the exclusive formula by faith alone. This is disconcerting enough. But it is one of the most macabre aspects of the dispute about the Joint Declaration that the Lutheran apologists -- bishops, church officials, members of church assemblies, even professors of theology -- justified this step by saying that Melanchthon had already left out the exclusive formula by faith alone in the article on justification in the Augsburg Confession. And since Melanchthon made the claim concerning the teaching of the first 21 Articles of the Augsburg Confession that it was 'not contrary or opposed to . . . [even that] of the Roman Church' (BC, 47), they said that it was not only permitted, but in point of fact required to remove the exclusive formulae from any consensus of both churches reached today. What are we to say to this? As it is, the exclusive formula is lacking in the Augsburg Confession, Article IV. But in the next article but one, on 'The New Obedience', it says, using a quotation from the early church, that we have 'forgiveness of sins . . . through faith alone' (BC, 32_. And in the article which is so decisive for the issue of justification, on 'Faith and Good Works', we read that our reconciliation with God 'happens only through faith' (BC, 42). Since, as Melanchthon thought, the first twenty-one articles are also acceptable to the Roman Catholic Church, we ought to be able to say from the Lutheran perspective that the sola fide formula is acceptable ecumenically. But what about Trent? A number of Lutheran apologists who drafted the Joint Declaration apparently feel more strongly bound to it than to the Augsburg Confession.
Even if the Lutheran's were to affirm the JDDJ, the Reformed Churches may not approve of the JDDJ due to it's Osianderian form of Lutheran that John Calvin rejected in the Institutes of the Christian Religion in his debates with Andreas Osiander. As an appendix, here's a footnote where Jüngel's disapproval of Osianderianism is briefly addressed:
No doubt Calvin was also influenced by this insight when he refuted Osiander's doctrine of justification. The latter countered Melanchthon's concept, which saw justification as purely imputed, by saying that justification is a making righteous (iustum efficere), not only in the presence of God, but also in us, thanks to an indwelling of the righteousness of Christ (inhabitatio iustitiae Christi).
Jüngel's conclusion is to Hans Küng's solution in Justification is a weak Maybe? and an adament No! to the Joint Declaration on the Doctrine of Justification.
Related: Doctrine of Justification, Eberhard Jüngel, Hans Küng, JDDJ, Joint Declaration, Joint Declaration on the Doctrine of Justification, Justification, Justification: The Heart of the Christian Faith, Karl Barth, Pope John Paul II