Defining Unity in Faith

Yesterday (19th May 2025), Pope Leo gave an address to 'Representatives of other Churches and Ecclesial Communities, and Other Religions' (which you can read here). 

It was interesting seeing the term 'Ecclesial Communities' in both title and address. I don't know its origin but I do remember the controversy it caused when the Congregation for the Doctrine of the Faith* used it in its declaration Dominus Iesus in the year 2000 (read the document here).

The document, signed by the CDF's Prefect, the then Cardinal Ratzinger, stated that 'Churches' are those Christian bodies that have a valid apostolic succession and Eucharist while 'Ecclesial Communities' are those that do not. Hence, Orthodox Churches are indeed Churches while Protestant bodies like the Church of England et al are Ecclesial Communities. This did not impress members of the latter.

The reason I am writing about the Holy Father's address, however, is on account of the following. In the third paragraph, he states that,

My election has taken place during the year of the 1700th anniversary of the First Ecumenical Council of Nicaea. That Council represents a milestone in the formulation of the Creed shared by all Churches and Ecclesial Communities. While we are on the journey to re-establishing full communion among all Christians, we recognise that this unity can only be unity in faith. As Bishop of Rome, I consider one of my priorities to be that of seeking the re-establishment of full and visible communion among all those who profess the same faith in God the Father, the Son and the Holy Spirit. (emphasis added)

'we recognise that this unity can only be unity in faith'. When I first read this, I wondered what he meant by this. I have always thought that when the Church talked about seeking unity with other Christian groups she meant corporate unity, that is to say, other Churches - and Ecclesial Communities - accepting the primacy of the pope and essentially becoming part of the Catholic Church. Here, though, Leo seems to be saying that the unity we are seeking is something else, a 'unity in faith'. 

I am not at all sure that I am reading this correctly because surely we already have unity in faith. What is our faith? Christ crucified. All Christians by definition believe that He died for us therefore in that sense we are already united with one another. 

But clearly, Pope Leo does not regard this as meaning any such thing. So, what does 'unity in faith' actually mean?

I have no answer to that question. However, Leo does go on to say that he seeks 'the re-establishment of full and visible communion among those who profess the same faith in God the Father, the Son and the Holy Spirit' so that sounds like the corporate unity that I thought we were looking for. As with his (re?) definition of the word doctrine that I mentioned previously, I'm sure I will keep my ears open for anything more he says about this topic.

*Now called the Dicastery for the Doctrine of the Faith