The homily begins with a reflection on divine mercy and the fact that grace is not cheap. It came at the price of the crucifixion.
In an address given in Jerusalem in 1994 at the invitation of Rabbi Rosen, Ratzinger described Christ's crucifixion as an "act endured in innermost solidarity with the Law and with Israel”, and he noted that the crucifixion was the perfect realisation of what the signs of the Jewish Day of Atonement signify.
As he explained, all sacrifices are acts of representation, which, from being typological symbols in the Old Testament, become reality in the life of Christ, so that the symbols can be dropped without one iota being lost:
The universalising of the Torah by Jesus, as the New Testament understands it, is not the extraction of some universal moral prescriptions from the living whole of God's revelation. It preserves the unity of cult and ethos. The ethos remains grounded and anchored in the cult, in the worship of God, in such a way that the entire cult is bound together in the Cross, indeed, for the first time it has become fully real. 
"Encountering Christ means encountering God's mercy," Joseph Ratzinger stressed in his homily.
The first Good Friday was the ultimate Day of Atonement
Christ, who makes an offering of himself on the Cross, is therefore the true and eternal high priest anticipated symbolically by the Aaronic priesthood. To borrow a phrase from the Oxford Professor of Poetry, Geoffrey Hill, the crucifixion was "no bloodless myth."
The Atonement of Christ, as both the eternal high priest and sacrificial victim, not only fulfils the Old Testament in the sense of transfiguring its symbols into a new reality; it also gives rise to a new sovereignty, a new kingship.
The first Good Friday was the ultimate Day of Atonement, and the cross was, as St Augustine suggested, a "mouse-trap" for the devil. Christ set the Cross as a trap with his blood for bait, with the result that the devil, having shed the blood of one who was not his debtor, was forced to release his debtors. However until Christ's triumphal return at the end of the world, the devil will contest this sovereignty and incite the mob to worship other gods, to engage in various forms of idolatry.
Only a mature faith can withstand the ideological challenges of the present, Ratzinger warned.
This leads to a second theme in the homily, the dictatorship of relativism. When Christ’s sovereignty is contested other “gods” take His place. When the human ego, the human self, itself becomes its own god, there is no longer any transcendent truth or goodness or beauty, all becomes subjective, all becomes relative to the experience of the self.
The idolatry of the self, the worship of one’s own ego, started to become commonplace in the nineteenth century. With this came the idea that the God of Judaism and Christianity was defunct. The works of Ludwig Feuerbach (1804-1872), provide a very powerful example of these currents of thought. In The Essence of Christianity Feuerbach argued that God is only the sum of the attributes that make up the greatness of man. He declared that the true atheist is not the man who denies God, the subject; it is the man for whom the attributes of divinity, such as love, wisdom and justice, are nothing. 
Feuerbach influenced a whole raft of anti-Christian revolutionaries including Karl Marx (1818-1883), Freidrich Engels (1820-1895), Nikolai Bakunin (1888-1938), and Nikolai Chernyschevski (1828-1889). In his Theses on Feuerbach, Marx declared that the only point on which he did not agree with Feuerbach is that he attached too much importance to nature and not enough to politics.
Frontal assault on Christianity
The Nineteenth century reached the peak of its anti-Christian development in the works of Friedrich Nietzsche (1844-1900). Nietzsche believed that Christianity, though on the wane in European culture, would continue to be influential unless and until scholars turned their attack on Christian ethics. Prior to Nietzsche there had been a tendency for scholars to focus their criticisms on apparent scientific inaccuracies in the bible, but they had not directly attacked Christian ethics. In 1888 Nietzsche wrote:
Up to the present the assault against Christianity has not only been fainthearted, it has been wide of the mark. So long as Christian Ethics are not felt to be a capital crime against life, their defenders will have the game in their hands. The problem of the ‘truth’ of Christianity – the existence of its God or the historicity of its legend, to say nothing of its astronomy and its natural science – is in itself a very sudsidiary problem so long as the value of Christian ethics go unquestioned. 
In the latter half of the twentieth century, especially from the late 1960s onwards, this Nietzschean dream has been in the process of being realised. It provides much of the intellectual infrastructure for what the then Cardinal Ratzinger called the ‘dictatorship of relativism’. We live in a culture where truth itself is the subject of ridicule and reason is held in suspicion.
In his homily, Ratzinger urged his confreres in the College of Cardinals not to be afraid of the spirit of the present age, however anti-Christian it may be.
A third theme in the homily is that a mature faith is not tossed about by such waves of ideology and their summons to idolatry. A mature faith does not flinch in the presence of wave after wave of intellectual attacks on the Church, on Christian revelation, on the belief in truth, in goodness and in beauty.
Being a mature Christian is not merely giving one’s assent to a list of theological propositions, it is about participating in the very life of the Holy Trinity in the sacramental economy. It order to arrive at a mature faith one therefore needs to be open to receiving the gifts of the Holy Spirit and to participating in the growth of the Body of Christ through the reception of sacramental graces.
All forms of idolatry stand in the way of such growth to maturity. Ratzinger mentions that money, buildings and even books do not last forever.
How are Christians to live under the "Dictatorship of Relativism"?
A final theme of the homily is that the fruit of one’s life work that endures beyond the drama of death is this: ‘all that we have sown in human souls: love, knowledge, a gesture capable of touching hearts, words that open the soul to joy in the Lord’. This is the “baggage” each person may carry to the customs house of eternity. This is what ultimately matters.
Ratzinger’s mentor Hans Urs von Balthasar ended his book Romano Guardini: Reform from the Source with the statement:
It is possible that Christian loneliness will be terrible in the future because love will disappear from the world’s general disposition. The challenge that lies before us is the “courage of the heart” particularly since Christians know that the sacrifices must be made in such a way that they transcend the world into an incalculable fruitfulness.
"An 'adult' faith is not a faith that follows the trends of fashion and the latest novelty; a mature adult faith is deeply rooted in friendship with Christ." (Joseph Ratzinger)
In other words, Balthasar understood that those who live under the dictatorship of relativism may feel lonely and battered so they need courage. They need a mature faith, not a faith that bends to the changing winds of the Zeitgeist.
The pain of loneliness is not worthless
The pain of their loneliness is not however worthless. It may be offered up for those who have lost the ability to love. In this way it can become the source of an incalculable spiritual fruitfulness. Under the loveless intellectual confusion of the dictatorship of relativism and its blindness to beauty, we are all, in a sense, Carmelites, though Benedictine beauty, wherever it is found, is a deep source of consolation.
In making this speech to the College of Cardinals prior to his own election, Cardinal Ratzinger was exhorting his fellow Princes of the Church not to be afraid of the Zeitgeist, however anti-Christian it might be. They need the courage of a mature faith that does not despair in the darkness of the night.
This message is not only of relevance to those who hold high ecclesial office but for all Christians who must live within a social milieu and work within institutions where ideological warfare has replaced reason and civility and where power plays have replaced loving service.
The author, Professor Tracey Rowland, Doctor of Theology, is a Roman Catholic theologian who teaches at the University of Notre Dame in Australia. Rowland has been a member of the Vatican's International theological Commission since 2014. In 2020 she was awarded the Joseph Ratzinger Prize.