“Private” Masses. I’ve never attended one. I stumbled across one once, traversing a sacristy at a college staffed by a men’s religious order. I quickly exited, experiencing surprise, alarm, and a distinct sense of trespass.
Pope Pius XII restates some arguments of the 1940’s. I don’t know if these are accurate or complete, but here they are:
95. Some in fact disapprove altogether of those Masses which are offered privately and without any congregation, on the ground that they are a departure from the ancient way of offering the sacrifice; moreover, there are some who assert that priests cannot offer Mass at different altars at the same time, because, by doing so, they separate the community of the faithful and imperil its unity; while some go so far as to hold that the people must confirm and ratify the sacrifice if it is to have its proper force and value.
My sense with the matter: they are of no concern to me. I’m not invited. I’m not obliged to assist with them. If they have spiritual value, it happens without my cooperation and certainly without my agency. They don’t require my approval. They will not be sunk by my thumbing them down.
96. They are mistaken in appealing in this matter to the social character of the eucharistic sacrifice, for as often as a priest repeats what the divine Redeemer did at the Last Supper, the sacrifice is really completed. Moreover, this sacrifice, necessarily and of its very nature, has always and everywhere the character of a public and social act, inasmuch as he who offers it acts in the name of Christ and of the faithful, whose Head is the divine Redeemer, and he offers it to God for the holy Catholic Church, and for the living and the dead.[Roman Missal, Canon of the Mass] This is undoubtedly so, whether the faithful are present – as we desire and commend them to be in great numbers and with devotion – or are not present, since it is in no wise required that the people ratify what the sacred minister has done.
If MD 96 is true, it is a matter of God’s grace first.
Mass should have at minimum, a server:
97. Still, though it is clear from what We have said that the Mass is offered in the name of Christ and of the Church and that it is not robbed of its social effects though it be celebrated by a priest without a server, nonetheless, on account of the dignity of such an august mystery, it is our earnest desire – as Mother Church has always commanded – that no priest should say Mass unless a server is at hand to answer the prayers, as canon 813 prescribes.
I was not asked to transform from trespass to service some thirty years ago. I haven’t been asked since. Consult the full document Mediator Dei on the Vatican web site here.