When we talk about “mystery,” there’s first a distinction or a clarification we need to make between the “popular”[1] definition of mystery and the “ecclesial”[2] definition of mystery.

            The popular definition of mystery is that it’s something which cannot be defined; that is, the word can be defined, but not the thing which is the mystery itself. And so, when a person hears the word “mystery,” the first images that come to mind are: the unknown, a problem to be solved, a detective story, murkiness, hiddenness, and secrecy. A mystery, therefore, can be exciting to plunge into, or it can provoke a sense of foreboding and dread.[3]

            The ecclesial definition builds upon the popular definition. And so, in the world of Church, mystery is something hidden or secret which has been revealed. Revelation is the key difference. In some ways, a mystery—in the ecclesial sense—doesn’t even sound like a mystery (because it’s not hidden anymore). But the Church still calls this “revealed something” a mystery for two reasons.  Firstly, a revealed mystery isn’t necessarily universally known; not all people have faith in divine revelation, and so for those people, ecclesial mysteries remain mysterious (in the popular sense of the word). And, secondly, even for people of deep faith, the revelation of a mystery doesn’t mean that the full depth and breadth of a mystery has been exhausted; the mystery or mysteries are infinitely deeper and richer than our capacity to receive them. And so, even with the revelation of a mystery, there's always more to be revealed and known; the quality of mystery still remains.

The Mystery and mysteries

            A further distinction needs to be made with ecclesial mysteries; specifically, that there is “mystery” and also “The Mystery.” On one hand, a mystery is some act of God: some action he initiates which helps us along the way of salvation. We call actions “mysteries” because they reveal God’s hidden intentions to us: that through Christ we would be raised up and restored to life in him forever.[4]  For example, thus far, the mystery referred to in this essay has been God’s active drawing us to himself; that draw or call is an action God has undertaken.

            On the other hand, the Mystery (with a capital M) refers to God himself: the Holy Trinity and each divine Person therein. But caution should be exercised in not making too sharp of a distinction between “mystery” and “the Mystery”. This is because the mysteries by which God draws us to himself (for example, Baptism and Reconciliation) are like the hands of God at work among us. A ”mystery” and the “Mystery” are intertwined. Nonetheless, we make some distinction between the One who initiates the mysteries, and the mysterious actions themselves through which we are drawn back to that One. Consider a person who writes a book; he or she is distinct from his or her writing, but yet, that person’s imprint is found throughout the book. There’s an inseparable connection between the writer and what’s written, but there’s still a distinction.

            And so, in this essay, it should be noted that “the Mystery” (with a capital M) refers to the Mystery of God himself, while “mystery” or “mysteries” refers to some action of God through which he draws us to himself and makes real the good news of salvation.

[1] Popular meaning “of or relating to the general public.”

[2] Ecclesial meaning “of or relating to the Church.”

[3] This dual sense of mystery brought about the phrase mysterium tremendum et fascinans; that is, “the terror and fascination of mystery.”

[4] Dei Verbum, 2: “In His goodness and wisdom God chose to reveal Himself and to make known to us the hidden purpose of His will (see Eph. 1:9) by which through Christ, the Word made flesh, man might in the Holy Spirit have access to the Father and come to share in the divine nature (see Eph. 2:18; 2 Peter 1:4).”