Over at Rocco's place...

Full marks for this post.

This however, is much less satisfactory. Personally, I've never been able to buy into the kneejerk revulsion for Cardinal Kasper exhibited by some commentators. Doubtless he and the then Cardinal Ratzinger were located on differing places of the theological spectrum and it's no secret that my sympathies have tended to lie with Ratzinger. However, I've always thought that Kasper should be paid the same respect that I would demand that theological opponents of Ratzinger should pay him. Both are serious Catholic theologians, and the presumption must be made that they are aware of the gravity of their roles as Cardinals of the Church and that they know enough not to lead the Church into heresy. That doesn't mean agreeing with everything either of them say, but it does mean the strong presumption that their statements fall within the allowable spectrum of theolgical discourse.
Now, the news report on which Rocco bases his post is worth reading. However, I think that his analysis of Kasper's position is wrong. Rocco says:

So everything that we keep hearing screamed about as dogma and "the most
important things in the life of the church" every day has just been clarified --
by a cardinal of the church who's not a self-anointed anything, no less -- as
being on the tier of mere "ethical problems," "not on the top of the hierarchy
of truths" should not obstruct the greater good of unity, so long as the
participants don't get all self-righteous and make themselves impediments to
it.

What Kasper actually says is:

He told a press conference at Ushaw that the differences in how Christian communities are dealing with ethical matters were not automatically church-dividing; "we have to see if they are differences in pastoral approaches or doctrinal differences, " he said.

What he is saying is that these ethical questions can be church-dividing; what needs to be done is to discern whether were are talking about a difference of pastoral approach or of doctrine.
With regards to the issue of doctrine, it's important to call to mind John Paul II's Evangelium Vitae.

EV 57 Therefore, by the authority which Christ conferred upon Peter and his Successors, and in communion with the Bishops of the Catholic Church, I confirm that the direct and voluntary killing of an innocent human being is always gravely immoral. This doctrine, based upon that unwritten law which man, in the light of reason, finds in his own heart (cf. Rom 2:14-15), is reaffirmed by Sacred Scripture, transmitted by the Tradition of the Church and taught by the ordinary and universal Magisterium.
On Abortion he says
EV62Given such unanimity in the doctrinal and disciplinary tradition of the Church, Paul VI was able to declare that this tradition is unchanged and unchangeable. 72 Therefore, by the authority which Christ conferred upon Peter and his Successors, in communion with the Bishops-who on various occasions have condemned abortion and who in the aforementioned consultation, albeit dispersed throughout the world, have shown unanimous agreement concerning this doctrine-I declare that direct abortion, that is, abortion willed as an end or as a means, always constitutes a grave moral disorder, since it is the deliberate killing of an innocent human being. This doctrine is based upon the natural law and upon the written Word of God, is transmitted by the Church's Tradition and taught by the ordinary and universal Magisterium.
No circumstance, no purpose, no law whatsoever can ever make licit an act which is intrinsically illicit, since it is contrary to the Law of God which is written in every human heart, knowable by reason itself, and proclaimed by the Church.
On Euthanasia he says
EV65 Taking into account these distinctions, in harmony with the Magisterium of my Predecessors and in communion with the Bishops of the Catholic Church, I confirm that euthanasia is a grave violation of the law of God, since it is the deliberate and morally unacceptable killing of a human person. This doctrine is based upon the natural law and upon the written word of God, is transmitted by the Church's Tradition and taught by the ordinary and universal Magisterium.
Depending on the circumstances, this practice involves the malice proper to suicide or murder.

What that boils down to is that the Church infallibly teaches the value of human life and the immorality of abortion and euthanasia. That's not simply doctrine, it's an infallibly taught moral dogma.
By Kasper's criteria, material difference on these specific issues would seem to be a sufficent obstacle to Church Unity. We're not talking about pastoral approaches. We're dealing with doctrine.
I think Rocco's difficulty arisies with the common misunderstanding of the term 'hierarchy of truths'. This does not mean that some aspects of revealed truth are more or less true. Rather, it's an acknowledgement that some of these truths are more or less central to the Christian Faith. However, as the Directory on Ecumenism notes:

75. Moreover, the "hierarchy of truths" of Catholic doctrine should always be respected; these truths all demand due assent of faith, yet are not all equally central to the mystery revealed in Jesus Christ, since they vary in their connection with the foundation of the Christian faith.
[...]
176. The question of the hierarchy of truths is also taken up in the document Reflections and Suggestions Concerning Ecumenical Dialogue:
"Neither in the life nor in the teaching of the whole Church is everything presented on the same level. Certainly all revealed truths demand the same acceptance of faith, but according to the greater or lesser proximity that they have to the basis of the revealed mystery, they are variously placed with regard to one another and have varying connections among themselves".

That means that we can acknowledge that what unites Christians is greater than what divides them, and we can make progress on the basis of the great issues that unite us without throwing the lesser truths as an obstacle to cooperation. However, the Roman Catholic Church cannot set aside these lesser truths as the Divine Revelation is a unity and the abandonment of even the least of these truths would damage the whole.
As Catholics we are called to have confidence in the unified and consistent nature of revealed truth and that dialogue with our seperated brethern on the basis of the greater truths of Christianity will lead to understanding of those truths which are lower on the hierarchy of truths. What we do not admit is any notion that there can be a more true or a less true when dealing with the Deposit of the Faith.
(As an aside, I would note that the place of a particular teaching on the hierarchy of truths does not depend on the solemnity with which it has been taught by the Magisterium. For example, the Assumption of the Blessed Virgin and the Infallibility of the Roman Pontiff have been taught in the most solemn ways possible. However, that does not place them at the top of the hierarchy of truths.)
Ultimately, what Kasper is describing is a great tragedy. There have been some great advances on the level of dogmatic theology (agreement with the Luterans on Justification, a recognition by some Protestant groups of the necessity of a teaching authority) but the hope that this might inspire is being shattered by an increasing difference on ethical matters, and Kasper does not seem to be arguing that we can set these aside easily.
I'll leave the final word with Cardinal Kasper:

Called to be holy, Cardinal Kasper said, the church also is called to be prophetic, to listen to the world, to understand its hopes and struggles and to offer guidance and hope based on the Gospel.
"The dividing lines which have unfortunately become evident on ethical issues since the latter half of the last century are therefore not secondary or irrelevant for an understanding of the nature of the church," he said.
"In touching on holiness, they touch on the essential nature of the church itself," the cardinal said.
Cardinal Kasper acknowledged that Christian communities that, for example, have ordained women to the priesthood or have decided to bless homosexual unions have done so out of a belief that they are exercising a prophetic role in society and demonstrating God's love, acceptance and call to all people.
However, he said, Christian communities must act in continuity with the faith of the Gospel and the earliest Christian communities.
"We should not imagine that we possess more of the Holy Spirit today than the church of the early church fathers and the great theologians of the Middle Ages," he said.