Is the Anaphora of Addai and Mai ... which lacks an Institution Narrative and thus does not include the Words of the Lord ... a valid Consecration of the Most Holy Eucharist?
Rome has given the answer Yes; but not all people in the Traddisphere trust what modern Rome says. But very reliable writers from before the Council came to the same conclusion. Eric Mascall did ... and I have come across the following, in an unpublished and very interesting letter of Dom Gregory Dix shown to me by Mrs Jill Pinnock, where I'm sure the great mystagogue has A and M in mind: "What are the minimum requirements for [eucharistic] validity? I suppose (1) a priest (2) bread and wine (3) the words of institution (I personally would reduce this last to any plain indication that the rite now being performed with the bread and wine by the priest is intended as a deliberate fulfilment of the command at the Last Supper, touto poieite eis ten anamnesin mou. A repetition of the words of institution is the most compendious and unambiguous, and best authorised, way of doing this)."
There is an important theological point here,
It has become axiomatic that the Lex Orandi should prescribe the Lex Credendi. You want to know what the Catholic Church teaches? Look at the words with which the Catholic Church prays.
Pius XII tried to fudge this distinction. A pity. I disapprove of the notion that what we believe (which can vary quite a lot as theological fashions morph) can or should license us to us mess around with the words Tradition gives us in the Liturgy. This error lies at the basis of the mistakes made in the post-Conciliar period, when committees in Rome arrogantly presented to themselves the competence to change whatever they wished.
There are two distinct methodologies in conflict here.
One ... call it the a priori ... works out from scratch ... from theological basics ... what a liturgical formula should be or should include.
The other ... the historical ... looks at what actual liturgical phenomena have actually said or done over two actual millennia; and makes that study its basis.
Much more Traddy, in my opinion.
Much safer for us, if we have to endure any more 'creative' pontificates.