VATICAN CITY — Just days before the Ordinary Synod of Bishops on the Family began in Rome, Muhammad Ali was honored in his native Louisville, Ky., commemorating the 40th anniversary of his third fight with Joe Frazier — The Thrilla in Manila — on Oct. 1, 1975. Ali is aged now, but the memories of his three fights with his fellow American, the 1975 bout breaking the tie in Ali’s favor, are still vivid. The commemoration on the eve of the synod brought to mind two other heavyweights — German theologians, not American boxers — who have been battling on and off for decades.

Indeed, as Synod 2015 proceed towards its third week, it is remarkable how it is tracking the three major theological battles between Walter Kasper and Joseph Ratzinger: holy Communion for the divorced and civilly remarried, the ecclesial status of Protestant communities and the relationship between the universal and local Churches.

In 1993, Kasper, like Ratzinger, a gifted academic theologian appointed a diocesan bishop in Germany, issued a pastoral letter advocating admitting the divorced and remarried to holy Communion. Ratzinger, then prefect of Congregation of the Doctrine of the Faith, rejected Kasper’s claim in no uncertain terms, approved by St. John Paul II.

In 1999, John Paul appointed then-Bishop Kasper secretary of the Pontifical Council for Promoting Christian Unity. When, during the Great Jubilee of 2000, Cardinal Ratzinger published the declaration Dominus Iesus, teaching that Jesus alone is the unique Savior of mankind and that the Catholic Church alone is the fullness of the Church he founded, Bishop Kasper was publicly critical. So great was the criticism, fanned by Bishop Kasper, that John Paul took the unusual step of voicing his support for Dominus Iesus at a Sunday Angelus address, making it clear that, in the sharp conflict between the two Curial Germans, it was Cardinal Ratzinger who spoke for the Pope. Demonstrating rather impressive magnanimity, John Paul elevated Bishop Kasper to the cardinalate a few months later and appointed him president of the Pontifical Council for Promoting Christian Unity in March 2001.

The early years of the new millennium then brought a respectful, if pointed, argument between Cardinal Ratzinger and Cardinal Kasper in theological journals about the nature of the Church. Cardinal Ratzinger argued that the universal Church was prior to the local Churches, while Cardinal Kasper took the opposite view. It was the third high-profile disagreement between the two.

All of which would only be history but for the events of March 2013. In choosing to abdicate on Feb. 28, Benedict graciously permitted Cardinal Kasper to participate in the conclave to elect his successor. Had he waited less than a week, until March 6, Kasper would have been 80 and barred from entry on grounds of his age. It was during the conclave preparations that Cardinal Kasper gave Cardinal Jorge Mario Bergoglio his book on mercy, which in turn the new Pope Francis publicly praised during his first Angelus address.

To those with Roman ears to hear, it was at least curious, if not astonishing. Not yet a week elected, Pope Francis selected one cardinal for praise to a worldwide audience, and it was the one most known over two decades for public conflict with Ratzinger/Benedict. It was not lost on the College of Cardinals that with Benedict less than two weeks into retirement, Pope Francis was highlighting the work of his longest and most vocal critic in the Curia. Unlike Ali-Frazier, the battles of the past would not be left there, but revived between the now-octogenarians.

In February 2014, the Holy Father would invite Cardinal Kasper to address the consistory of cardinals wherein he reiterated his 1993 proposals. After his proposals were resoundingly rejected by the vast majority of the cardinals who spoke, Pope Francis came to his public defense the next morning, inviting Cardinal Kasper to address the consistory again. Not a few cardinals were curious as to the reasons such papal favor was being bestowed on the retired cardinal most famous for public clashes with Benedict.

More than 18 months later, the three Kasper-Ratzinger fights are taking center stage at Synod 2015. Unlike Ali-Frazier 40 years on, it is not just about commemorations, but current contestations.

The first issue — holy Communion for the divorced and civilly remarried — has, after a mighty push from Cardinal Kasper and the synod managers, apparently failed. The letter of 13 cardinals to Pope Francis at the beginning of the synod, arguing that entertaining such a proposal would threaten the Church’s fidelity to the word of God, prompted the Holy Father to state emphatically the next day that doctrine could not be touched by the synod. It remains to be clarified whether or not the current practice is doctrinal or disciplinary, but the idea that it is only disciplinary would require the synod to reject the clear teaching of St. John Paul II after the 1980 synod on the family and of Benedict XVI after the 2005 synod on the Eucharist.

The second issue, regarding the status of the “separated brethren” in the Protestant communities, has received little attention thus far at the synod. But the instrumentum laboris, using the convenient language of “some say,” offers a proposal that non-Catholics married to Catholics might receive the Eucharist regularly (128). The current practice is that such spouses, if they share the faith of the Catholic Church in the Eucharist, may receive holy Communion in cases of “grave necessity.” The synod’s working document proposes that the very fact of the mixed marriage itself constitutes a perpetual grave necessity, meaning a type of de facto intercommunion would be introduced. Given that Eucharistic Communion is the fruit of ecclesial communion, such an innovation would practically revise the status of the Protestant communities — touching precisely on the debate between Cardinal Ratzinger and Cardinal Kasper over Dominus Iesus in 2000.

Finally, the third issue relates to the relationship of the universal and particular Churches, the subject of that theological debate between Ratzinger and Kasper. Cardinal Kasper argued the local Churches were primary, giving rise to the universal Church, while Ratzinger held that the Church universal exists first, from which local Churches are established. The issue is relevant at the synod, as it is proposed that, on various difficult issues, local Churches will be left to make their own pastoral applications.

It is the fallback position of the Kasper proposal. If holy Communion for the divorced and remarried cannot be had universally, then perhaps it could be had locally, as Kasper himself attempted to do in 1993, when he was a bishop of Rottenburg-Stuttgart. As that prospect has emerged at the synod, strong voices have emerged to oppose it. Cardinal Jorge Urosa of Caracas spoke to the Register to oppose it; the primate of All Ireland, Archbishop Eamon Martin of Armagh, publicly opposed it; and Archbishop Stanislaw Gadecki, speaking in the name of all the Polish bishops, rejected any modification of the current practice. The “local option” approach would, therefore, lead almost immediately, if adopted, to contradictory practices on either side of the German-Polish border. Sacrilege on one side would be a means of salvation on the other, a solution which, whatever else it might be, could hardly be called “catholic.”

Cardinal Kasper has kept a relatively low profile at Synod 2015, in contrast from last year, when he was giving interviews almost daily. Benedict XVI is in seclusion. They are retired. There are no personal rematches between them. But their battles dominate the synod.

Father Raymond J. de Souza is the editor in chief of Convivium magazine.

He was the Register’s Rome correspondent from 1998 to 2003.