The theology and practice of the Eucharist is undoubtedly at the heart of the ecumenical task. The discussions on intercommunion and eucharistic hospitality have become the focus of nearly every ecumenical dialogue and of many ecumenical gatherings. Nevertheless I do not want to discuss this issue again here. For I am convinced that there will be no serious answer to the problem as long as we do not agree on some basic ecclesiological principles.

I want to deal with one of these basic principles. It is very strange indeed that so few theologians or churchmen have written on the link between Eucharist, Baptism and Church taken all together. Usually one studies the relation of Baptism with Church, of Eucharist with Church, of Baptism with Eucharist, but without putting together the result of these three analyses. I shall try to do it here. It will lead us to the very basic question of the distinction between the oneness (unicitas) and the Unity (Unitas) of the visible Church.

On Thursday, 4th October, 1979 James Mackey, formerly Professor in the Department of Theology and Religious Studies in the University of San Francisco, delivered his inaugural lecture as Thomas Chalmers Professor of Theology in the University of Edinburgh. The lecture hall in New College, the Divinity Faculty of the University, was filled to overflowing. Undoubtedly it was Professor Mackey's reputation which had drawn many members of his audience to hear him. Strange to say, that reputation was established not by any of his written works, nor by any extensive familiarity with his personal biography. What had attracted some, at least, of his hearers was his appointment having been the subject of an unprecedented debate in the General Assembly of the Church of Scotland in May of this year.