When challenged that women’s ordination and homosexual  marriage were grave obstacles to unity between Catholics and Anglicans, an Anglican priest countered by saying, “Let’s not forget the obstacles to unity of the dogmas of the Immaculate Conception and Papal Infallibility.”

At first this seems a reasonable response for the Catholic Church does indeed demand assent to these two doctrines which many Protestants either deny completely or wish were mere pious opinions. But can we really compare the issues of homosexual marriage and women’s ordination with the dogmas of the Immaculate Conception and Papal Infallibility? I think not, but before I discuss them in particular it is worth thinking for a moment about what we mean by ‘church unity.’

Catholics do not mean by ‘church unity’ simply the reconciliation of two estranged groups. Neither do we mean the kind of ‘shared communion’ and ‘recognition of ministries’ that has been achieved between Anglicans and Lutherans. We mean something more than that.

When we say ‘unity’ we mean formal, visible unity between previously estranged  individuals and groups, but we believe that unity is not found through concordats, treaties and carefully negotiated settlements. Instead we are united together in the same faith. We are united in the fullness of the historic Christian faith. We are united together in the apostolic faith. We are united together in the fullness of the same faith once delivered to the apostles. It is the sharing in the fullness of this same faith that provides our unity. We do not just desire unity of form while tolerating diversity of doctrine. We believe true unity is unity of form and doctrine.

This is very different than the mutual tolerance of different opinions that the Anglicans speak of when they think of unity. It surprises me, therefore that theologian with the breadth of learning and intelligence of the present Archbishop of Canterbury should attempt to recommend this rather shallow understanding of church unity to Catholics. The Catholic understanding of Church unity is far more profound and organic than a mere confederation of contradictions–which is the Anglican muddle model.

This brings me to these two particular doctrines of the Immaculate Conception and Papal Infallibility. Catholics understand these two doctrines to be central to the fullness of the Christian gospel, and see them clearly set out in the gospel itself. That they were defined later is only evidence that it was only in later days that the doctrines were doubted, and therefore needed to be defended and defined.

The Immaculate Conception is there in the realization that the Blessed Virgin was ‘full of grace.’ If sin is the lack of God’s glory, (“all have sinned and fallen short of the glory of God”) and grace is the gift of God’s glory, then Mary who was full of grace was also empty of sin. It only remains to ask when that sinlessness began and we conclude that it began when her life began. Thus, even if one disagrees with this interpretation, it is at least arguable that the doctrine of the Immaculate Conception is folded not only into the gospels itself, but into a coherent and complete understanding of the doctrine of the Incarnation. It is, if you like, part of the original deposit of the faith.

Can this be said or even argued about the issue of homosexual marriage? No. This is a radical departure from every strain of Christian and Hebrew moral teaching at all times and in all places. It is impossible to argue that homosexual marriage is even a permissible part of universal and primitive Christian teaching.

Similarly, Papal Infallibility is folded neatly into Christ’s commission to Peter: “You are Peter and on this Rock I will build my Church and the gates of hell will not prevail against it.” It is arguable, and part of ancient and continuous Christian tradition that this verse not only establishes the Petrine Primacy, but also it’s implicit infallibility: “The gates of hell will not prevail against it.” Again, while one may disagree with this interpretation, it is impossible to disagree with the historical fact that this  is an interpretation held by most Christians at most times in most places down through the ages. Therefore, like the doctrine of the Immaculate Conception, it is a stepping stone to a profound unity in the church –not just a handshake with neighbors, but a way in to a deep sharing in the fullness of the faith.

We need to contrast this, like the contrast with homosexual marriage, with women’s ordination. This too, is a radical break from the whole Hebrew-Christian tradition. It is not part of the core of the gospel, it is not part of the ancient tradition. It is not part of the continued tradition, and any interpretations of the Scriptures or theological justifications for this innovation are novelties.

We can see  therefore that the doctrines of the Immaculate Conception and Papal Infallibility take us deeper into the core of the gospel and the ancient tradition whereas homosexual marriage and women’s ordination are a radical rupture with the same.

Consequently, while it may appear that the four issues are obstacles, in fact the first two are actually stepping stones to unity. The second two are stumbling blocks.