Subsistence

Subsistent Relations: A Preface to Understanding the Trinity & Divine Simplicity Together

Introduction

The concept of subsistent relations is a pivotal yet nuanced idea in Catholic theology, essential for understanding two central doctrines about the divine nature. First, the doctrine of divine simplicity expresses God as the ultimate reality—free from internal division or multiplicity—emphasizing God’s absolute oneness and establishing the framework for classical monotheism. Second, the doctrine of the Trinity reveals that God is not just a single essence but also a communion of three distinct Persons—Father, Son, and Holy Spirit—each fully God, yet without compromising that oneness.

This raises a fundamental question: How can God be absolutely one in essence and yet exist as three distinct Persons without introducing division or multiplicity? The term subsistent relations is crucial for beginning to answer this question because it provides the conceptual tools needed to explain how the Father, Son, and Holy Spirit are distinct Persons who fully possess the one divine essence without adding to or fragmenting it.

Originating from the Greek term hypostasis, which refers to a concrete and self-standing reality, the Latin tradition developed this into subsistentia, emphasizing how each divine Person exists as a fully realized, relational identity within the unity of God’s essence. Subsistent relations articulate how the Father, Son, and Holy Spirit are not mere modes, parts, or roles but unique, self-standing relational identities that fully express and possess the one divine essence.

By establishing that each Person is a distinct yet inseparable reality within the single divine essence, subsistent relations serve as the necessary framework for understanding how the Trinity does not contradict divine simplicity. They show that the distinctions in God are grounded in relational identity rather than division. This lays the groundwork for deeper theological reflection on how God can be both one and tri-personal.

However, this framework does not solve every aspect of the mystery. Future explorations will delve into five key principles that harmonize the doctrines of the Trinity and divine simplicity in full, showing how subsistent relations lay the essential foundation for addressing this profound question.

For now, understanding subsistent relations as a coherent way of speaking about how the divine Persons exist and relate within God’s oneness is a critical first step. It opens the door to further inquiry: If each Person fully possesses and expresses the one divine essence, what implications does this have for our understanding of God’s unity and relationality?

Understanding Subsistent Relations: A Framework for the Reality of the Trinity

The term subsistent relations refers to the idea that each divine Person is a real, self-standing relational identity within the one divine essence. While it might seem paradoxical to describe a relation as something that “subsists” or “stands on its own,” this term emphasizes that the relations in God are not external attributes or mere roles but are intrinsic and essential to what it means to be the Father, Son, and Holy Spirit.

In this framework, the Father is not merely related to the Son; He is Father precisely in being the Father of the Son. Similarly, the Son is not a separate entity who is merely connected to the Father; His very identity is to be the Son, eternally begotten by the Father. The Holy Spirit is the Love proceeding from the Father and the Son, fully possessing the divine essence in His unique relational identity.

To clarify this concept, consider three foundational principles that frame the understanding of subsistent relations:

Each Relation Is the Divine Essence Itself

Each Relation Fully Possesses the Entire Essence

The Relations Are Rooted in Revelation

Principle 1: Each Relation Is the Divine Essence Itself

The first principle establishes that the relations are not separate from God’s essence; rather, they are the divine essence itself, existing in distinct relational modes. The Father is the divine essence as “begetting” the Son. The Son is the divine essence as “begotten” by the Father. The Holy Spirit is the divine essence as “proceeding” from the Father and the Son. This means that the distinctions among the Father, Son, and Holy Spirit are real, but they do not add anything extra to God. The Father is not a “part” of God; He is the one divine essence as Father.

This avoids the mistake of thinking that the Persons of the Trinity are like parts of a whole. Each Person is the fullness of God but in a distinct relational identity.

St. Thomas Aquinas captures this idea, stating:

“Relation really existing in God is really the same as His essence and only differs in its mode of intelligibility. Thus, relation and essence do not differ from each other but are one and the same.”  

(Summa Theologica, I, q. 28, a. 2)

Aquinas explains that while the Father is not the Son (because “Fatherhood” and “Sonship” are distinct relations), both are entirely the same divine essence. The relations are not accidental properties but are subsistent—they exist in and of themselves as the divine essence.

Principle 2: Each Relation Fully Possesses the Entire Essence

The second principle affirms that each Person fully possesses the one, undivided divine essence. This guards against any idea that the Father, Son, and Holy Spirit “share” the essence in the way that three siblings share the same genetic material. Instead, each Person is the divine essence, existing in a distinct relational identity. This understanding helps prevent any interpretation that the Persons are three “parts” of God or that they each possess a “piece” of divinity.

Thomas Aquinas states:

“The essence is not diversified by the relations but is one and the same in each Person.”  

(Summa Theologica, I, q. 39, a. 1)

This means that the Father, Son, and Holy Spirit are not three parts of God but each one is fully and entirely God. The Son is everything that the Father is, except being the Father; the Holy Spirit is everything that the Father and Son are, except being the Father or the Son.

The Catechism of the Catholic Church affirms:

“The divine unity is triune… The divine persons do not share the one divinity among themselves but each of them is God whole and entire.”  

(Catechism, 253, 255)

Principle 3: The Relations Are Rooted in Revelation

The third principle grounds the concept of subsistent relations in the context of divine Revelation. While human reason can help clarify and articulate the distinctions within the Trinity, it cannot generate them. We know the Father as Father, the Son as Son, and the Holy Spirit as Spirit because Scripture reveals these relations to us, not because philosophical speculation alone could lead us there. This principle ensures that the language of “subsistent relations” is not just a philosophical exercise but a way of faithfully describing the reality of God’s inner life as disclosed in Scripture.

For example, the Son is revealed in the Gospel of John as the “only-begotten Son”:

“No one has ever seen God; the only Son, who is in the bosom of the Father, he has made him known.”  

(John 1:18)

Similarly, the Holy Spirit is described as the one who “proceeds” from the Father and the Son:

“But when the Counselor comes, whom I shall send to you from the Father, even the Spirit of truth, who proceeds from the Father, he will bear witness to me.”  

(John 15:26)

Thus, subsistent relations are not just abstract distinctions but real identities that reflect God’s self-revelation in Christ and the Holy Spirit.

Richard of St. Victor emphasizes the necessity of relational plurality for the fullness of love:

“For in a pair of persons, the perfection of each requires union with a third, for only in this shared love is the fullness of joy realized.”  

(De Trinitate, Book III, Chapter 11)

He suggests that the ultimate fulfillment of joy and love necessitates the presence of a third Person, reflecting the perfect communal nature of divine relationality in the Trinity.

Implications of Subsistent Relations

Understanding the Trinity through the lens of subsistent relations has several important theological implications:

Preservation of Divine Simplicity

Avoidance of Modalism and Tritheism

Relationality as Core to Divine Life

Scriptural Coherence

Subsistent relations provide a coherent way to interpret the Scriptural language of “Father,” “Son,” and “Holy Spirit” without reducing these identities to mere metaphors. They are real distinctions that exist within the unity of the divine life.

Biblical References:

John 17:21:  

“That they may all be one; even as you, Father, are in me, and I in you, that they also may be in us.”  

Jesus’s prayer highlights the intimate relationality within the Trinity. The Son is “in” the Father and the Father is “in” the Son, suggesting that the oneness of God is a oneness of relationship, not just of substance.

1 John 4:8:  

“Anyone who does not love does not know God, because God is love.”  

The statement “God is love” implies that love is essential to God’s very being. Love requires a lover, a beloved, and the act of loving, corresponding to the Father, the Son, and the Holy Spirit as the bond of love. This scriptural testimony aligns with the idea that relationality is intrinsic to the divine essence.

Conclusion

The concept of subsistent relations offers a robust and accessible way to understand the unity and distinction within the Trinity. By affirming that each Person is a real, self-standing relational identity who fully possesses and expresses the one divine essence, this framework preserves both divine simplicity and the reality of the Trinitarian distinctions. Rooted in traditional theology and Scriptural revelation, the language of subsistent relations provides a way to speak about God that is faithful to the Christian understanding of the Trinity as a mystery of one God in three Persons.

As Joseph M. Dalmau notes:

“In explaining the question about the divine relations and personalities, it helps to note how much one must consider the ‘great analogy’ that comes from the supreme perfection of God… For the opposite opinions seem to come from too much assimilation and, as it were, univocation of divine realities with created things.”  

(Sacrae Theologiae Summa IIA: On the One and Triune God, p. 446)

Understanding subsistent relations as a coherent way of speaking about how the divine Persons exist and relate within God’s oneness is a critical step. It opens the door to further inquiry into the profound mystery of how God can be both one and tri-personal. By exploring this concept, we begin to grasp the implications for our understanding of God’s unity and relationality, ultimately leading us into deeper contemplation and appreciation of the divine mystery.

References:

Aquinas, Thomas. Summa Theologica.  

Catechism of the Catholic Church.  

Dalmau, Joseph M. Sacrae Theologiae Summa IIA: On the One and Triune God.  

Holy Bible, Revised Standard Version.  

Richard of St. Victor. De Trinitate.