Imagine a grand old church like St. Peter in Rome. Over the altar is the grand round dome while below the floor plan is square and angular. This is not just the work of interesting architecture. It all means something. Circles that have no beginning or end represent things eternal, represent heaven, represent God. Things that are squarish represent earthly things, man made things, man. That these two shapes come together right were the altar sits is making a point. When we celebrate the Mass, heaven and earth are colliding like that which powers the Starship Enterprise with matter and anti-matter coming together. (Other versions would be a square nave and an apse for example.)
Particularly for Catholics, this is essential theology. When we celebrate The Mass, we don’t celebrate one at St. Sebastian at 9:00AM, one at St. Vincent at 11:00, and one at St. Bernard at noon though it appears to us that we do. There is only One Mass being celebrate around the world and throughout time.
That is also why when we speak about the Body of Christ, we include the entire Church; militant, penitent, and triumphant. The Body cannot be cut in twain even by death. The bride is united and alive in the Bridegroom with Whom she is One causing the whole body to be alive as one, death not being like a severed hand left on the ground - or conversely, that those who have not been born into the next life yet not being a branch on the vine. So we are always somehow mysteriously connected in Christ.
One of the glorious things about St. Sebastian Parish is that the walls are lined with depiction of saints. I often think as we are heading into the heart of the Eucharistic prayer of the saints (official and otherwise) showing up and joining those in the pew to offer oblation to our Father. There may be only a few hundred at Mass, but it is standing room only once everyone shows up from angels to toddlers. A Catholic church is like one of those mysterious buildings that are much larger on the inside than they are on the outside.
Understanding that things like time and space work differently in the next life, it is easy to imagine the whole of God’s children coming together in concert for the Wedding Feast of the Lamb. And it makes even more sense that we may all pray for each other; we on earth praying for each other and for the Church Penitent, the Church penitent praying for themselves and for the Church militant, and those in heaven praying for all of us to come to perfections as the Bride of Lamb with them in our heavenly inheritance.
This all leads us to today’s subparagraph g of paragraph 79 of the GIRM. Another important aspect of the Mass is the intercessions, and by it, I believe we are not just talking about the general intercessions, but all of the intercessions that take place during the Mass. They are sprinkled all over the place like pepper from a grinder on your salad at a nice restaurant. “For all your children scattered throughout the world,” and “For our departed brothers and sisters,” just to name a couple “by which expression is given to the fact that the Eucharistic prayer is celebrated in communion with the whole Church, of both heaven and of earth, and that the oblation is made for her and for all her members, living and dead, who are called to participate in the redemption and salvation purchased by the Body and Blood of Christ.”