“What a difference a day makes,” sang Dinah Washington. And why? Because “24 little hours / Brought the sun and the flowers / Where there used to be rain.” But sometimes, we know, it just keeps raining. So, it depends on the day, doesn’t it?

What about a word? What difference does a word make? Maybe not much. My grandparents said, “keen.” But now “cool” is de rigueur. (Honk if you like “way cool.”) Of late, I’ve been reading Charles Dickens’s comical The Pickwick Papers (1837). Here’s a curiosity: He uses “personation” in a positive sense rather than “personification.”

But sometimes a word makes a staggering difference. Benedict XVI, in his Regensburg address, calls attention to the Greek word logos. Remember that John’s Gospel begins with the Good News that “In the beginning was the Word (logos)” (John 1: 1). On Benedict’s view, “The encounter between the biblical message and Greek thought did not happen by chance.” No, it was providential.

For months now, I’ve been puzzling over the concept “subsistence,” from subsistencia, the Latin approximation of the Greek hypostasis. It suggests, roughly, a mode of being that enables something or someone to act in accord with its nature. Jacques Maritain, an eminent Thomist, admits that subsistence gives students “many headaches.” And you are right, gentle reader, a blog post shouldn’t induce headaches! But let’s consider, only briefly, a pair of questions that involve subsistence. Vatican Council II’s Lumen Gentium tells us that the Church of Christ, “constituted and organized as a society in this present world, subsists in the Catholic Church.” It adds that “elements of sanctification and truth can be found outside her structure” and that they “impel towards Catholic Unity.” The more ecumenical term “elements” replaces the earlier term “vestiges” (from the Latin vestigia).

How can we best understand “subsists”? Jacques Maritain offers important context. On his view, the Church has a dual subsistence. She has a “natural subsistence,” namely that “of the human persons who are her members,” as well as a “supernatural subsistence” that transcends her natural subsistence. He finds support for his position in St. Paul’s teaching on the Mystical Body of Christ.

Maritain also links the subsistence of the Church to its personality. The soul of the Church, forming one body, bears the image of Christ. On this account, he writes that the Church receives “a true subsistence—perfectly one itself and sealing the whole in its unity—which is the metaphysical foundation of the personality of the Church.” After Vatican II, Joseph Ratzinger would offer still more context. He explained that “Subsisting is a special case of being. It is being in the form of a subject standing on its own.” So it is that, however wounded, the Church is a singular reality: the Sacrament of Christ’s presence.

Let’s turn now to a second theological question. John’s Gospel also tells us that “the Word was with God, and the Word was God.” St. Thomas Aquinas designates God as Ipsum esse subsistens, that is, “subsisting being itself.” Why is this? God of His essence is uniquely and absolutely self-subsisting. In God alone does esse, the act of being, inhere in His essence. For this reason it is entirely suitable that we speak of Him as Ipsum esse subsistens. To be sure, this term has an adamantine abstractness. Even so, it reflects our profound reliance on a Creator who reveals Himself as “I Am Who Am” (Exodus 3: 14). No wonder that Scripture urges Creation to “Sing to the LORD a new song; sing to the LORD, all the earth” (Psalm 96:1). He is the same, yesterday, today, and forever. Not just sometimes, but through all the ages and into eternity.