I think that the OP knows what the words Requiem aeternam mean. I suspect the question is about the theological meaning and purpose of the various prayers that use this sort of language, as there is an Anglican cleric who questions this.
Lindsay54, I will cut to the chase, as I come from a background similar to yours. The Requiem texts are predicated upon the existence of purgatory, pure and simple. The texts presuppose that the departed soul is there, and we pray for quick deliverance of that soul–and by extension, all departed souls who have not been beatified or canonized–into heaven. Your vicar probably suspects this, and the p-word makes him uneasy. After all, if a soul is already in heaven, he/she does not need our prayers, and if in hell, then is beyond our prayers.
Anglican theology has traditionally recognized an intermediate state, which is largely its basis for the prayers for the departed. However, this theology, while rooted in a few writings by the Anglican Divines, really was not developed until the Oxford Movement held sway, and in the period after World War I. In England, the realization of the horrors of that conflict made it politically correct to pray for the dead, as it was an outlet for the sorrows wrought by the Great War. Liturgical revisions in the 1920s began to provide for prayers for the departed.
These naturally did not specifiy purgatory, and for low and broad churchmen, these prayers were/are more of a commemoration than anything else. This gave rise to names of the departed being read on All Saints Day. It was a sort of liturgical equivalent to the many mermorials, plaques, and other inscriptions where one sees “In memory of…” But the high churchman–who actually during the late 1800s had gradually begun celebrating Masses for the Dead, with black vestments, observing All Souls Day, etc.–understood these prayers to refer to the intermediate state, a somewhat tepid, though still accurate, term for purgatory. When many Anglo-Catholics began using missals in the early 1900s, these missals included the texts for the Masses for the Dead. Naturally, nearly all of these texts were taken in their entirety from the Roman Missal, which made the existence of purgatory clear through the Requiem texts. This situation was made more difficult by the fact that the liturgical funeral texts of the Vatican II era, particularly their English translations, reduced some of the purgatorial imagery (no more* Dies Irae*), used white vestments, etc. These were not erroeneous changes, by any means, and they still presuppose the presence of the departed in purgatory, but their general tone and the accompanying trends of “instant canonization” eulogies at Catholic funerals has in many ways worked against the notion of praying and sacrificing for the dead.
Many Anglicans, even of the of the Anglo-Catholic variety, do not even realize that the Requiem texts in the English Missal, Anglican Missal and American Missal all are Roman in origin and, as such, these texts entirely convey the nature of the Church Expectant/Suffering. They do not connect the dots, so to speak. A minority of Anglo-Catholics do grasp this, and their notion of praying for the departed is informed by this understanding. They realize that the Church is divided into the Church Militant on earth, Church Suffering (or Expectant) in purgatory and the Church Triumphant in heaven, and they pray for each. A handful may even utter the dreaded p-word (such as the Order of the Holy Cross in the US, whose classic St. Augustine’s Prayer Book used that term). Catholics of all stripes also understand that if we pray for the repose of a soul who is not in purgatory, then another soul or souls will receive the graces resultig from those Masses and prayers. This is all part of what we mean when in the Apostles Creed we say that we believe in the Communion of Saints.
I suspect that your vicar may be a little squeamish about this because he does not accept, or at least is unclear on, the nature of that intermediate state, purgatory.
