The question often arises whether, and if so to what extent, a truth of faith that is supernatural not only in its manner but also in its content, i.e., a mystery (mysterium), can be defended under the light of reason. This is particularly true for the dogma of the Holy Trinity, which is not only misunderstood but often misinterpreted, not just by non-Christians who reject the tenet, but even by Christians themselves, including Christian theologians.
Therefore, we can turn for help to nothing but the "perennial philosophy" (philosophia perennis), that system of intellectual knowledge validated by its intrinsic passive cause, which alone deserves the name philosophy and alone is worthy of being the Handmaid of the Queen, that is, theology. Although this system solidified nearly three-quarters of a millennium ago, both in terms of time and geography, its every tenet is reducible to the principle of non-contradiction, thereby excluding the possibility of error under the light of natural reason. Its truth is thus independent of time and place—hence eternal.
What does the dogma of the Holy Trinity state?
- God is one in essence and three in person: Father, Son, and Holy Spirit.
- Is this not a contradiction?! Three equals one?! 1 + 1 + 1 = 1?!
- No! It is three times one in one: 1 x 1 x 1 = 1!
A contradiction arises only if we affirm something ("A") and its negation ("not-A") at the same time and in the same respect. Clearly, that is not the case here. Nature answers the "what" question—"What is this being?"—referring to a being’s objective essence. A person, however, answers the "who" question—"Who is this being?"—referring to a being’s subjective essence. Unity pertains to nature, while plurality pertains to persons.
It is true that in the empirical world we do not encounter instances where the objective and subjective aspects of a being are numerically distinct. Hence, we cannot imagine or conceive of such a thing. If we attempted to, we would either form a notion that these three persons are merely three modes of manifestation of the same deity above the trinity of persons (as held by the modalists, i.e., the ancient Sabellians and medieval adherents of Eckhart), or we would begin to speak of three gods (as in the tritheistic conception of Roscellinus of Compiegne). Both are found in various religions and thus would not be unique to Christianity. The former is exemplified by the Hindu concept of the "triple mask" (trimūrti), and the latter by the divine triads of various religions.
A further critical question arises: Even if it can be proven that this is not a contradiction, can it also be proven that we cannot, on this basis, speak of a "holy duality" (Binity) or a "holy three-million-two-hundred-sixty-thousand-four-hundred-fifteen," but only of the Holy Trinity? In other words, can it be proven that if God has a plurality of persons, this plurality must consist only of three?
Let us examine the question in detail.
In the case of God, we speak of a single substance (substantia). What is substance?
Substance is nothing other than the ultimate bearer of the perceptible properties (accidentia) of an individual being. Its existence cannot be directly apprehended through sensory knowledge but is known only through its properties with the help of the intellect. The intellect recognizes or demonstrates the existence of substance through abstraction and inference, employing the principle of sufficient reason (principium rationis sufficientis), which is reducible to the principle of non-contradiction.
What does the principle of sufficient reason state?
Everything that exists necessarily has a sufficient cause. Sufficient reason is the existential principle that directly and independently establishes why a particular being is the way it is and not otherwise. For example, while the four equal sides of a square are fundamental to its "squareness," they are not sufficient cause. Only in combination with four right angles does the square exist; otherwise, it could be another kind of rhombus. Anyone who denies or doubts this principle implicitly acknowledges it because denying or doubting it would itself require a sufficient reason; otherwise, such denial or doubt would be baseless. This would lead to a contradiction. Thus, if only properties existed—i.e., beings that exist in something else—they would lack sufficient reason for their existence and therefore would not exist. Hence, it is certain that substances, in addition to properties, exist in the objective world.
Are there non-material substances?
The specific object of human intellectual cognition is being as being, abstracted from perceptible things (Ens ut ens in quidditate sensibili, S. Th. p. I., q. LXXXIV., a. 1). Humans derive the universal concept of being from perceptible things, and thus, in our earthly existence, our intellect can reliably and objectively recognize spiritual beings only through perceptible phenomena. Consequently, such knowledge is limited, allowing us only negative and analogous concepts of spiritual beings. These include the ideas that they are "non-material" and that they are independent of space and time.
By applying the principle of sufficient reason, we recognize that human activity involves both spatially and temporally dependent elements and those independent of space and time. The latter include our ability to recognize universal (spatially and temporally independent) concepts, known as universals (universalia), through intellect, and the spiritual freedom arising from this, known as will. Activities independent of space and time must have a principle of existence that is itself independent of space and time, which cannot be explained by our body, as it is bound to space and time. Thus, there must be a principle of existence within humans that underlies these activities: this we call the soul. However, the soul is not a full substance, as it, together with the body, constitutes the human being. No activity of ours is purely bodily, nor purely non-bodily, as even our concept formation begins with sensory perception provided by the body. Therefore, the human soul can be more precisely defined as a being—independent of space and time—that, together with its corresponding body, underlies the human being’s properties.
Angels, on the other hand, are purely spiritual beings whose soul is a substance that independently underlies angelic intellect and will. Hence, in angels, there is a real distinction between substance and accidents (substantia et accidentia), potentiality and actuality (potentia et actus), and consequently between essence and existence (essentia et existentia).
In God, however, no real distinction is possible. Through the Proofs of God’s existence (cf. Quinque viæ), it is certain that no real (as opposed to merely conceptual) distinction can exist in God that undermines His nature as pure actuality (actus purus). Thus, no real distinction between potentiality (potentia) and actuality (actus) can be posited in Him. If God had any parts that divided His essence, this would imply potentiality. For instance, if a real distinction between substance and accidents were posited in God, these would metaphysically constitute parts. One part—substance—would lack the actuality of the accidents, while the other part(s)—the accidents—would lack the actuality of the substance. Consequently, God would no longer be pure actuality. Thus, no real distinction between substance and accident, or between essence and existence, can exist in God.
This truth, discernible even in philosophy, aligns with traditional Jewish and Muslim understandings, which likewise reject the Trinity on the grounds that it implies a real distinction incompatible with the doctrine of pure actuality (actus purus). They regard the Trinity as unreasonable, arguing that it introduces real distinctions that would divide God’s essence and lead to a form of association (shirk) or composite nature in God.
Let us revisit the key statement.
In God—as is indisputable through the proofs of God’s existence—there can be no such real and non-imaginary (realis sed non virtualis) distinction that undermines His nature as pure actuality (actus purus), i.e., that posits a real distinction (distinctio realis) between potentiality (potentia) and actuality (actus) within Him.
The emphasis here is on the word such! The question is whether a such real distinction is possible in God that, while being a real distinction, does not create a real distinction between potentiality and actuality in the divine substance.
Imaginary (virtualis) distinctions are possible in countless instances within God. The divine essence is identical to its manifestations; thus, the metaphysical claim, proposed within the Byzantine hesychasm tradition, that a real distinction exists between God’s essence (οὐσία / essentia) and His activity (ἐνέργεια / actus), is erroneous. Such a claim would posit a real distinction between essence and existence within God, which would mean we could no longer speak of God as pure actuality. Because the distinction between essence and existence in God is merely imaginary, the divine essence can be interchangeably referred to using its “attributes,” unlike created beings: God is Love, God is Goodness, God is Truth, God is Beauty, God is Justice, God is Mercy, etc.
According to the universal Christian perspective, however, a real distinction exists between the divine Persons. Is this not a contradiction? Is this not blasphemy? Is this not “association”?
Thomas Aquinas demonstrated comprehensively that, based on the principle of non-contradiction, there is only one type of real distinction possible within God that is identical to the divine essence yet does not result in its division (S. Th. p. I, q. XXVIII, a. 2 and a. 3).
To understand this, we must examine the objectively certain categories of beings.
Categories demonstrate the real division of real beings. We have already identified two fundamental categories: the categories of substantial and accidental beings. The former are those capable of existing independently, without a subject, while the latter cannot exist on their own but only within other beings in the created world. These accidents can be of two types: those existing within their subjects (internal accidents) and those existing externally (external accidents). Internal accidents can also be subdivided: those that increase the substance’s being in itself, or absolutely (absolute accidents), and those that do so in relation to other substances (relative accidents). Absolute accidents include those that augment the matter (materia), such as quantity (quantitas), and those that augment the form (forma), such as quality (qualitas). Relative accidents, on the other hand, enhance a substance’s being not in itself but in its relations to other substances; these are called relations (relatio). We will not elaborate on external accidents here.
Relations (relatio) can again be of two kinds: those arising from a being’s essence (relatio transcendentalis) and those arising from a being’s accidents (relatio accidentalis).
A transcendental relation does not differ from the essence of the being itself but is implicit within it and thus is not truly an accident. Such a relation exists, for example, between matter and form, or between potentiality and its specific actuality. This can take two forms: in a real relation (relatio realis), the related thing is a real being (ens reale) in the objective world, whereas in a logical relation (relatio logica vel rationis), the related thing exists only in the intellect (ens rationis vel virtualis vel idealis).
An example of a relation that is identical in essence yet distinct in reality is the relationship between New York and Boston. The distance between the two cities is the same—say, 215 miles—but the directions (New York to Boston vs. Boston to New York) are opposite, making them truly distinct in reality.
In God, four such relations (relationes) can be posited that are opposed to each other, meaning they are truly distinct from one another, yet each separately possesses the divine essence without division (S. Th. p. I, q. XXVIII, a. 4). It can be demonstrated that as a spiritual being, God has two kinds of internal activity identical to His essence, which can give rise to relations: understanding (intellectus) and willing (voluntas). Consequently, within each of these, two relations can be posited.
On the intellectual level, there exists the relation of understanding and being understood. God perfectly understands Himself. This understanding and the being understood, though individually identical to the divine essence, are truly distinct from one another due to their opposed directions.
On the volitional level, there exists the relation of loving and being loved. God necessarily wills, i.e., loves, the infinite good, which is Himself. His self-love and being-loved, though each individually identical to the divine essence, are truly distinct from one another due to their opposed directions.
Among these four relations, those that constitute "Persons" (relationes subsistentes), or "subsisting relations," are those which express unique relations independent of the others. Before proceeding further, it is important to clarify the concept of "Person."
What is a "person"?
A person (persona) is the designation of a primary and complete substance that is independent of other substances not only in its existence but also in its activities (understanding and willing). The basis of its substantiality (subsistentia), or independence of existence, is personality. The four existential independencies of a person are as follows:
- It does not rely on a subject for its existence, as it is a substance.
- It does not depend on particular attributes for its existence, as it is a primary substance, not a secondary one endowed with such attributes.
- It does not depend on another partial substance for its existence, as it is a complete substance.
- It does not depend on another complete substance for its existence, as it is itself a complete substance.
If, therefore, a person is autonomous and thus unique, unparalleled, and self-existent as a subject—which in the strictest sense can only be applied to a divine person—then of the aforementioned four relations, only three express unique, unparalleled, and wholly independent relationships. These are understanding, being understood, and being loved. Thus, the definition of "person" applies to these. The first constitutes the One whom revelation designates with the term "Father," the second the One known as the "Son," and the third—the common activity of the first two in a logical, not causal sense—constitutes the One known as the "Holy Spirit." From all this, it follows that if the Trinity exists, then the Filioque thesis, which asserts that the mutual love of the Father and the Son constitutes the Holy Spirit, is necessarily true. For if this were not the case, then the relationship between the Father and the Holy Spirit would not differ from the relationship between the Father and the Son, and thus it would not constitute a distinct person (S. Th. p. I, q. XXX, a. 2.).
The Father is unique in being unoriginated and in originating two persons (one independently, the other jointly); the Son is unique in originating from one person and jointly originating another person; the Holy Spirit is unique in not originating but in proceeding from two persons as a single principle of being through one single procession. If the Holy Spirit were to proceed solely from the Father, this would imply a fourth person, but such that no relationship would exist between the pairs of subjects in relation, which would contradict the indivisibility of God.
Finally, three important notes follow:
- The above exposition does not prove the existence of the Trinity—that is, that the one divine essence necessarily exists in three persons (S. Th. p. I, q. XXXII, a. 1.). From the fact that the four aforementioned relations could form three divine persons, it does not necessarily follow that they actually do so. This actuality cannot be deduced based on the principle of non-contradiction; it can only be believed with certainty based on revelation, through the help of supernatural grace. However, it has been demonstrated that the doctrine of the Trinity is not unreasonable or absurd. Our supernatural faith in the Trinity does not contradict natural reason.
- The above reasoning demonstrates that if, as a consequence of God's spiritual nature, essence-identical divine relations exist and thus form persons, they can only form three (S. Th. p. I, q. XXX, a. 1.) and only in such a manner that the Son proceeds eternally from the essence of the Father through understanding, and the Holy Spirit proceeds eternally from the Father and the Son as a single essence through mutual love. A Trinity without the Filioque is thus a logical absurdity and cannot exist.
- These relations, unlike those of creatures, are not accidents but subsist in themselves, thereby constituting personalities (subsistentiae) that are distinct in reality, i.e., persons who wholly possess the divine essence and existence individually without division. Thus, the term "relation" does not apply univocally to both creatures and God but according to proper proportional analogy (analogia proportionalitatis propriae), with the difference between the two being infinitely greater than the similarity. Therefore, no form of subordinationist Trinity is possible, and all three divine persons must indivisibly possess the indivisible divine essence. It is worth noting here that both the Old Testament and the Qur'an speak of the "Word of God" and the "Spirit of God" in a subsistent relationship with "the" God. Thus, the question of "Trinity" within medieval rabbinical and Muslim theology was not dismissed offhand as an absurdity but emerged as a serious point of inquiry.
To illustrate the mystery of the Holy Trinity, I would like to draw the kind readers’ attention, as we near the end of this treatise, to a peculiarity of the German language. Through objectified speech in the third-person plural, I can speak of "someone," even of three persons, in the following forms:
- sie [they] – nominative case (Werfall / nominativus)
- sie [them] – accusative case (Wenfall / accusativus)
- ihrer [theirs] – genitive case (Wes[en]fall / genitivus)
- ihr [to them] – dative case (Wemfall / dativus)
However, through personalized speech in the second-person singular with respectful address, I can address "Someone," thereby entering into a relationship (relatio) and communicating (uniting) with "Someone" in the following forms:
- Sie [You] – nominative case (Werfall / nominativus)
- Sie [You] – accusative case (Wenfall / accusativus)
- Ihrer [Yours] – genitive case (Wes[en]fall / genitivus)
- Ihnen [to You] – dative case (Wemfall / dativus)
How interesting it is that, liturgically, the Holy Trinity as such is not typically addressed, yet its individual persons are. This is wonderfully reflected in this characteristic of the German language, where the two distinct forms of expression (objectively stating something about someone and personally addressing "Someone") are identical in form.
"God! God! God!"
In summary, under the light of pure reason, the following can be discerned:
- It is not a contradiction to assert that a single substance ("something," essence, nature) can be fully and indivisibly possessed by distinct persons ("someone," subject, bearer).
- This can only apply to a being of pure actuality (actus purus), i.e., God—a being in whom the dualities of potentiality and actuality (potentia / actus), essence and existence (essentia / existentia), and substance and accidents (substantia / accidentia) do not exist.
- If such a reality exists, it can exist only in three persons; there can be no "holy duality/Binity," "holy thirteen million," etc.
- If such a reality exists, it can only arise through the two processions of understanding and willing and in such a way that four relations are formed, which constitute three persons: the originless understanding person eternally begets the understood person, and the unity of their willing in one essence eternally breathes forth the third person, who does not originate others. Therefore, if such a reality exists, it can exist only as described in the Filioque thesis.
- A real distinction can exist only between the persons, not between the substance and the activity; thus, the hesychast thesis is false.
- All of this cannot be accepted through mere intellectual insight, for it is not self-evident under the light of natural reason that God is a Trinity. This truth can only be known through supernatural revelation and can only be accepted with certainty through the grace of supernatural faith.
- Natural reason can only demonstrate that the Christian doctrine of the Trinity contains no logical contradiction and that if the divine essence is possessed indivisibly by multiple persons, it can exist only as described in revelation: in three persons and in relationships where the originless Father, through intellectual activity, eternally begets the Son, and the Father and the Son, through a single act of will, eternally breathe forth the Holy Spirit.