Father Dwight Longenecker on Obstacles to Unity Between Catholics and Anglicans

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.

Read it all at his site.