Since the 1960's Walter Kasper has been diametrically opposed to the Joseph Ratzinger's cristal clear Catholic logical categories. In the wake of his Ratzinger's book Introduction to Christianity, Kasper accused Ratzinger of Platonism, i.e. basing his Christian outlook on the visible/invisible world distinction.
"Man's natural centre of gravity draws him to the visible, to what he can take in his hand and hold as his own. He has to turn round inwardly [what the Bible calls 'con-version'] in order to see how badly he is neglecting his own interests by letting himself be drawn along in this way by his natural centre of gravity. He must turn round to recognize how blind he is if he trusts only what he sees with his eyes. Without this change of direction, without this resistance to the natural centre of gravity, there can be no belief."
Introduction to Christianity, New York: Herder and Herder, 1970, 25.
"Kasper questioned Ratzinger's starting with the Platonic dialectic visible/invisible. He proposed an alternative: a historical-oriented theology, starting from the human being's concrete interwoveness with nature, society, culture and history. Different theological consequences would flow from such a starting point, he said. The meaning that we seek would then be mediated to us only through our concrete, historical encountering of the world and of people, or else not at all; and the result would be a far greater taking seriously of the concrete problems of people."
Joseph Ratzinger's Theological Ideas, James Corkery, SJ, New York: Paulist Press, 2009, 70.
Here we can see the philosophical undercurrents operative in a the Apostolic Exhortation Amoris Laetitia wherein the "ideal" world of the ten commandments, though acknowledged, is deemed unrealistic and therefore bracketed in favor of a purportedly more humane concession. The problem is more fundamental than theology. It is a problem of logic. What is wrong is wrong, no matter how you look at it or try to sugar coat it. Everyone has reasons for the sins he commits, but that does not make it right.
"The debate over the identification of the God of the philosophers with the God of the Bible was important to Ratzinger's early teaching in the field of fundamental theology. It would seem that Ratzinger attempts to avoid both the impersonal approach of Neo-Scholasticism and irrational voluntarism. The historical precedent for Ratzinger's identification fueled his renewed aprroach: for Joseph Ratzginger, the true God must be both rational and personal in ways that distinguish him from the product of pure speculation and the objects of superstition. He must be the God of Reason and the God of Faith if love and truth are to be united as the New Testatment teaches...For Ratzinger truth is not the product of human labor or consensus; rather it is something that can be unveiled--revealed--and discovered. Reason is the means by which human beings discover what God has revealed and come to understand the truth and to appropriate and apply it to their lives."
The Logos as Reason, Word, and Love in the Theology of Joseph Ratzinger, John J. Lynch, 2014, 28-29.
Faith and Morality are United in the Truth of God
"Faith's praxis depends on faith's truth, in which man's truth is made visible and lifted up to a new level by God's truth. Hence, it is fundamentally opposed to a praxis that first wants to produce facts and so establish truth. By holding on to the Creator, faith's praxis protects the creation against such a total manipulation of reality. By looking to the example of Jesus Christ, faith recognizes fundamental human values and rescues them from all manipulation. It protects man by protecting creation; the apostles' successors have an indestructible commission to maintain apostolic teaching and make it present.
"Since grace refers to both the creation and the Creator, apostolic exhortation (as a continuation of Old Testament admonitions) is involved with human reason. Contrary to appearances, the flight into pure orthopraxy, as well as the attempt to banish substantive morals from the realm of faith (with the teaching authority that is an integral part of the realm of faith), turn reason into a heresy.
"In the one case reason's ability to recognize truth is denied, and the renunciation of truth is elevated into a method; and in the other case faith is lifted out of the realm of reason, and rational considerations are not admitted as being possible components of the world of faith. Either faith is declared to be irrational, or reason is made out to be unbelieving--or both."
Principles of Christian Morality, Joseph Ratzinger (et alia), San Francisco: Ignatius, 1986, 70-71.
N.B. The above are the philosophical roots of The Proportionalism of Amoris Lætitia.
Ratzinger cites H. Küng's contention that Judeo-Christian morality has it's source in the cultures in which it first appeared, i.e. it is not from heaven but simply attributed by men to a divine authority. There is a fundamental difference of perspective here: man-made truth vs. truth really given and entrusted to man from God, accepted, promoted and defended on divine authority. The difference is between Theism and Atheism! Ibid., 49n.