Auctoritas, I believe, has more pull with a Traditional mind than mere Power. So I am going to ask:
How can one apply the the principle of auctoritas to the question of whether or not the eucharistic celebrant should face the people ... or deliberately not do so? I feel there are particular principles which have to be taken together.
The celebrant should face the East. This has enormous auctoritas, both in the archaeological evidence for the 'Orientation' [Eastfacingness] of church buildings and in early Christian writings. I will refrain from mentioning the enormous amount of learned 'Patrimony' literature establishing this, from the time when our 'Ritualists' were arguing for the 'Eastward Position' as against the then fashionable 'North End' custom. More recently, liturgists such as Michael 'Patrimony' Moreton re-established this truth, followed by Roman Catholics such as Cardinal Ratzinger and Dr Lang.
What I find very weakly evidenced - if it is at all - is the idea that it is important for priest and people to face in the same direction. 'Traddies' often overlook the fact that facing in the same direction is is not necessarily the same as facing East. Because ...
(1) some buildings, notably but not only the Roman basilicas, are specifically designed so that, by facing East, the celebrant thereby faces where the congregation has gathered. The rules of the Missal of S Pius V explicitly provide for what the priest does in such circumstances. The immemorial usage of the Urbs itself has great auctoritas, and so does the traditional praxis to which the Missal of S Pius V bears witness.
(2) some churches, particularly when built in confined urban spaces, are not built along an East-West axis.
Some 'traddies' try to get round the problem by cheerfully referring to something they are pleased to term 'the ritual East', as though it is at our disposal to pretend that East is wherever it is convenient for us to pretend that it is. I regard this as wholly frivolous. More important: early writers who emphasise the need to face East write about the need to face the Lord who comes to us from the East, and about the rising sun as his great Ikon. I do not think they would be impressed by a notion that East is wherever my whimsy takes me. The notion subverts any possibility of words meaning anything. Was it the Red Queen in Alice who said that she could make words mean whatever she wished them to mean? Just as many 'trendies' have what seems to me a sad fetich for always facing the people, some 'traddies' seem to me to have an equally unfortunate fetich for invariably having their backs to the people. I suspect that neither fetich would have been comprehensible, either to Easterners or Westerners, in the first Christian millennium.
But, unlike Kevin and Sharon, they did know where the EAST was.
Another principle with great auctoritas is the idea of the One Altar. Byzantine churches by prescriptive custom only have one altar (although they can consult practicality by adding parekklesiai; I regard the side altars in the side chapels of Latin churches as in effect parekklesiai too). This principle is bound up with important concepts such as the unity of God's people round his one altar celebrating his one sacrifice. To have an (unused) old altar up against the East wall, and another for actual use in front of it for the priest to stand behind, I regard as profoundly wrong, for theological as well as aesthetic reasons.
Where a church is Eastward facing and has an altar at the East end, the matter is perfectly clear. It is quite improper to move it or stand behind it. If the old altar has been shifted forward, it should be moved back. If an altar for versus populum has been placed in front of it, it should be got rid of. If it was made of wood, a parish bonfire would be a reverent way of disposing of a piece of furniture which has, remember, known the August Sacrifice.
Where a church is designed so that the sanctuary is at the West end, and the architect has structured the sanctuary so that the priest can thereby face East only by facing the people, my own view, which is not going to make me universally popular, is that he should do just that. I think not only of the Roman basilicas but, for example, of the Oratory and Blackfriars Churches in Oxford. As I mentioned, the ritus servandus in the Missal of S Pius V provides very explicitly for the celebration of Mass versus populum, and in my view ... not that anyone is likely to ask for it! ... this is what auctoritas suggests should be done. Versus Orientem rules OK.
But what about the Blackfriars' Church in Oxford? There the principle of One Altar is disastrously vitiated; a small modern table stands in front of the old majestic High Altar. Dunno. What do you think? My own gut feeling is ... go with the flow of the building as it is actually built; remove the little modern table, celebrate facing West, with the congregation facing West too ... although I would have to admit that the ancient Fathers would have had paroxysms if they could have seen both priest and people with their backs all turned in unison away from the East, away from the direction from which the Lord promises his Epiphany.
As regards churches built to face neither East nor West ... such as the Brompton Orsatory and Westminster Cathedral ... again, dunno. I am sure that the principle of One Altar should apply, so dump any coffee tables. Thank the Lord that the Brompton Fathers never messed around with their sanctuary and that Vin has restored the One Altar at Westminster. Again, my own, purely personal but quite strong, gut instinct is to go with the flow of the building as it was actually designed, and to celebrate with ones back to the people. But this is not facing East and does not have a great weight of auctoritas behind it.