What is the reason for the priests of the Latin rite to switch from the ‘ad orientem’ posture to facing the altar as done in the Holy Mass of Pope St. Paul VI after Vatican II

During Vatican II, the Church published a new version of the Mass for Roman Catholics known officially as the Mass of Paul VI, named such because he was the pope who promulgated (or published) it. It is sometimes referred to by other names such as the “Vatican II Mass,” “post-Vatican-II Mass,” or Novus Ordo (“New Order,” referring to the fact that it is the newest form of the Mass). To keep it simple, we’ll just refer to it as the Novus Ordo for the rest of this article!

The Novus Ordo is known as the “ordinary form” of the Mass in the Roman Rite. That means that it is the form of the Mass intended for common use and suitable for any liturgical context. This is in contrast to the “extraordinary form,” which would refer to forms like the Tridentine Mass; they can be used, but they are not treated as the “standard” form for the Mass.

One of the changes of the Novus Ordo was that priests celebrate the Mass versus populum, or “toward the people.” This is a change from what came previously, ad orientem (literally, “facing the east”). Both postures are acceptable but they emphasize different theological and liturgical points.

Ad orientem derives its name (“from the east”) from the fact that churches were often built so that everyone faced toward the east, toward the rising sun. Christ is referred to as the “rising sun” or the “dayspring.” His dawning upon us gives us new life. It also calls to mind the new morning of the Resurrection. Later on, churches were not always built to face east in this way, so the term instead came to refer to a more theological point. The priest, acting in the role of Jesus Christ the High Priest, leads the people to God and offers their sacrifice up to him. Ad orientem emphasizes the “flow” of our prayers from the congregation to the priest, and through the priest to God.

Versus populum instead emphasizes the flow of grace from God to the people. The priest still acts in the role of Jesus Christ the High Priest, but his posture now focuses on the fact that the sacrifice of Christ which he celebrates is given for the people. It also is a way of “centralizing” the altar as the focal point of the liturgy.

Neither of these two postures is inherently superior to the other. Versus populum is the standard for the Novus Ordo Mass, but in more recent years the Church has encouraged priests to use ad orientem as well, according to the needs and circumstances of their congregations. We should keep the theological significance of both practices in mind!As a final note, these practices refer specifically to the liturgy in the Roman (Latin) Rite. Other rites of the Church (i.e. Eastern Catholics) follow different rubrics. Some use ad orientem, some do not. Their reasons for doing so are similar in some ways to the Roman Rite, but there are bound to be unique reasons as well.