Deeper Dive into the Trinity
Updated: Jan 12
Discussing God is a very difficult task. Our knowledge and language is based on our experiences and sense data we receive from those things around us. However, God is outside of our normal experience. The Trinity is especially difficult to speak about precisely because it is so alien to our experience. This is not to say that we cannot know anything about God from natural reason, but, it does limit our knowledge of Him to his effects.
Although some may consider the use of reason of limited importance, all truth, whether revealed or natural, comes from God. Reason can be used to deepen our understanding of what has been revealed as well as demonstrating that sacred doctrine is not illogical. Natural sciences derive from human reason, which is limited by our knowledge and our intelligence . However, the objects of natural science are the world created by God and so, ultimately, they must point to their cause. Both natural science and reason are useful when discussing truths that are partially accepted by interlocutors. These means allow us to reach those who disagree with us and point them toward greater truths. Faith is a gift given by God but sacred doctrine can use human reason to make the truth clearer.
Aquinas did not think that God’s existence was self-evident to us like Anselm because we do not know his essence (nor can we by natural power alone), but that it could be demonstrated by His effects. In other words, we can reason from His effects to the cause, but not from the cause to the effects. This demonstration is not part of the faith, but a preamble to it that can be achieved through the application of natural reason. Aquinas reasoned that there were at least five ways to demonstrate God’s existence. There must be a first mover, a first efficient cause, and a necessary being. Additionally, there must be a cause of good, being and perfection as well as an intelligence that directs natural systems.
In addition to His existence, Aquinas taught that there were certain characteristics of God’s essence that could be known. First, God is completely simple which means that He is not composed in any way. Nor does God have any potentiality, but must necessarily be in act. On account of having no constituent principles, nor having a form or nature that is potential, there is no distinction between God’s essence and existence. This also means that God does not possess any accidental qualities (That is, He does not possess any changeable qualities) because he cannot be made actual in any sense. He is perfect because he does not lack any excellence. He is also perfect because all being is perfect as far as it is actual and God is fully actual. All things desire perfection and goodness is that which is desired. This means that God is good because He is “perfectly” perfect, and in fact, God is the only essential. God is also immutable, eternal, and absolutely one.
There is a great deal that could be said about this, but to be brief God is a perfect being. He is not composed of any parts. There can be only one perfect being because if there were two then they must be distinguished from one another in some way. This means that one of them would lack a perfection the other had or they would be the same being. If there is only one God and God has no parts, what do we mean to say when we say that the Trinity is one God in three persons?
In order to begin we need to clarify some terms. Essence, nature, and substance are closely related to one another. The essence of a thing is whatever is necessary to be that thing and also to distinguish it from other things. Nature connotes the same reality as essence, but with a logical distinction of acting or operation rather than being- so what it does rather than what it is. Substance denotes individual existence and the subject for any accidental properties, for example a board cut in half is still of the same substance with an accidental change in size, but a board burnt to ashes is subject to a substantially different mode of existence. When understood in human terms we can subtly differentiate these ideas although the differences may be virtual rather than real. A man can be said to be a rational animal that is composed of body and soul for a determined end, subsisting in an individual body and soul whose existence is contingent and not necessary. God, on the other hand, exists necessarily and is not composed of parts nor subject to change or accidental. His existence is not caused and does not differ from His essence and so there cannot be a real distinction in His essence, nature, or substance.
Boethius defined a person as a substance with a rational nature. Each person is individual, complete, endowed with intellect and exists independently. In the east the Greek term hypostasis came to convey the idea of personhood, although originally hypostasis often connoted the substance of a thing. St Basil distinguished hypostasis (individual and real) from ousia which signified the substance. Thus, person is really distinct from substance and essence. This distinction is critically important to understanding not only the Trinity, but related concepts such as the Incarnation and the hypostatic union.
If God’s existence is indistinguishable from his essence and there can be only one God, then how can three complete rational persons share this essence? In order to better understand, it is necessary to clarify what is meant by three persons with one nature. The persons of the Trinity are said to proceed which describes their relationship to one another. Most explicitly a procession explains the origin of one person from another. However, because God is a subsistent being origin is only analogous to what we mean when applied to contingent beings. There are no imperfections to be found in the divine processions and no diversity of nature. Rather than being external, these processions are immanent.
In corporeal beings actions are typically external. When I do something it happens outside of my mind and will. However, there are some kinds of actions which could be thought of as internal. For example, when my intellect understands an idea. These kinds of actions are immanent. A spiritual being has two kinds of actions: intellection and will. As such, God has two immanent actions that are internal which are to know and to will.
When creatures know themselves they apply a word self-referentially, but only in an accidental sense. However, God’s Word produces substantially and communicates the nature of the generator because in God there is no distinction between intellection and being. This Word is one, infinite, and such that no other is necessary because God’s intellection is perfect. This word generates likeness in nature without movement from non-being to being or potency to act. God’s Word proceeds as subsistence of the same nature which is generative and so the Word is begotten and the Son. This does not imply imperfection of any sort: the Son is not created nor does He depend on the Father as an effect depends on its cause. Rather, the Father communicates His nature and is the principle of origin for the Son. The Father is never other than Father and the Son is never other than Son.
When a man generates children, a child is produced as an external action whereas the child is an individual, independent substance from the father. His nature is communicated externally. The generation of the Word by the Father is not so. This generation is an internal action of intellect through which the Father begets the Son. Begetting implies an origin of a like nature, however, since God is in no way potential this action must be eternally actualized. The Son shares in the divine essence which is indistinguishable from the essence of the Father which is wholly identical because the infinite essence of God is not divisible and is not multiplied in this action. In God essence and existence are the same and so the Father and the Son are the same being. Yet, the Son is distinguishable from the Father as a subject. The one begotten is distinguished from the one who begets. The Father and the Son are two persons who share one divine nature.
In addition to intellection the other immanent action is volition. This volition is the procession of love and the Holy Spirit is the terminus of this procession in the same way that the Word is the terminus of the intellectual procession. Just as the divine nature is communicated by the intellectual action it is also communicated by the procession of love because of divine simplicity. This differs from the relation of generation because while intellect assimilates a thing to itself, the will is not assimilative and so we find two distinct processions in God. While the Son is generated from the Father alone, the Holy Spirit proceeds from both Father and the Son. This does not mean that there are two principles of origin, but this active spiration is common to the Father and the Son.
Finally, the Father has no principle of origin and proceeds from no one. Although all three persons know, the Father alone generates the Son by enunciating and each loves perfectly, but the love of Father and the Son spirate. In both cases, there is no distinction in nature, dignity or the like amongst the Father, Son, and Holy Spirit. The Divine Processions indicate how the three persons of the Trinity are consubstantial while being distinct in relations of origin.
So, there are two immanent actions which are intellection and will. These lead to four processions which are paternity, filiation, active spiration, and passive spiration. The processions describe the origin of the persons of the Trinity and the relations describe how the persons of the Trinity are related to one another from their origin. From the earliest days the Church has taught that the Father is God, the Son is God, the Holy Spirit is God as well as that the Father is not the Son, the Son is not the Holy Spirit, and the Holy Spirit is not the Father. Since they share a single nature, these persons must be distinguished by relation to one another. Just as with men, father is a word which describes the relationship with a child and so Father is not an essence of an action, but a relation between the Father and the Son.
Relations are not absolute like an essence, nor are they malleable like an accident (which God does not have in any case). These relations are eternal and unique to each person or in other words, they cannot be communicated to another. Rather, in God all things are one except where there is opposition of relation. The Son is begotten, but neither the Father nor the Holy Spirit are begotten. The Father alone is unbegotten. The Holy Spirit alone is spirated.
Even after positing that real relations exist in God it is not altogether clear what exactly it means to have a relation. In contingent beings real relations are accidental and understood as distinguishing one subject from another or ordered to the essence of a thing. If I become a father I have a real relation, but this relation is derived through reference to another and not a substantial change to myself. God is pure act and cannot have any accidental properties. Thus, for God the being of a relation must be actualized and identified with subsistent being itself. In the Trinity the divine relations exist by the existence of the divine essence. Since relations in God are substantial and not accidental the relation cannot be distinct from the divine essence.
If the relations were not the same as His essence then they would be creatures and not worthy of worship (Nor would they be God in any meaningful sense). Although the relation is not distinct from the divine essence it will be distinguished by reason. This distinction expresses a reference to something else such as the Father to the Son. The divine essence, at least by reason, contains the divine revelations because the divine essence is fully actualized.
In God essence and being are the same and therefore essence and being are common to the persons of the Trinity. These relations must communicate nature and being and this nature is subsistent. However, the relations are incommunicable because of the opposition of relations. Just as my son cannot be my father, so the Son is begotten and the Father is unbegotten. Son and Father share the same nature, but one actively generates and the other passively and so can be distinguished from one another.
In God the processions and relations are directly related. These concepts are implicitly revealed and progress toward a more distinct conception of God. The relations of God are founded on the processions. The persons of the Trinity are distinguished because of the divine processions and the opposition of relations entailed by those processions.
In both cases, the divine nature is communicated by intellection and volition. In God alone what is in God, is God and so the divine nature is necessarily communicated by any immanent procession. Both Son and Holy Spirit are of the same nature as the Father. There are only two processions because there are only two immanent actions. The Father generates the son (intellect) and the love of Father and Son spirate the Holy Spirit (will). These processions are the foundation of distinct relations in the Trinity.
The Father is the origin of the Son because the Son proceeds from Him. This entails a relation between the Father and the Son. In a like manner, the Holy Spirit proceeds from Father and Son. Hence, in God we find real relations of paternity, filiation, and spiration. Thus, we find three persons in the Trinity that are distinguished by relations opposed to each other, but not in nature.
A relation necessarily consists in reference of one thing to another which is relatively opposed to the other. In the case of the Trinity the opposition is relative which implies only distinction with a reference. Each person of the Trinity is opposed to one another in origin. The Father is unbegotten, the Son is begotten by the Father, and the Holy Spirits spirates from Father and Son. From this follows that there are four relations in God from the two processions, namely: paternity, filiation, active spiration, and passive spiration. Paternity and filiation are founded on intellection, while both kinds of spiration are founded on love.
Yet, if there are four relations it remains to be asked why there are only three persons in the Trinity. Paternity is relatively opposed to filiation, hence, the Father and the Son are distinct. Active spiriation is opposed to passive spiration and hence the Holy Spirit is distinct from the Father and Son. However, active spiriation is not opposed to paternity and filiation and so there is not distinction Therefore, there are only three relations opposed to one another.
Although we have focused on the internal actions of God, God is not limited to such actions. God also acts in external ways such as by creating the world. However, the Son and the Holy Spirit also have missions which extend supernaturally into the world. The processions are reflected in the missions of the Son and the Holy Spirit.
The mission of a divine person is a procession of one person to another with the purpose of a temporal effect. These missions reveal the divine processions because they “extend” those eternal processions into time. The Father sends the Son while the Father and Son send the Holy Spirit. Thus, the missions reveal to us that there is one God in three persons.
Each mission is related to the procession because there is equality between the one sent and the one sending. This does not imply a change on the part of the one being sent for the divine person does not begin to be in a place or cease to be where he was. Rather, the divine person exists in a new manner- which is entirely in the effect. These missions can be visible such as in the Incarnation and at Pentecost or invisible such as sanctifying grace.
While each mission is related to a procession which is eternal, they also have a temporal terminus. Neither the Incarnation nor the sending of the Holy Spirit on Pentecost are eternal for they occur in a specific place and time. Yet, their origin is eternal. The Divine Person is not changed in this sending but does become present in a new way. Hence, there is a two-fold procession (two-fold in terminus and not in principle) one of which is eternal and one of which is temporal. This mission must be from the eternal origin because a divine Person cannot be sent by command or counsel because they are in no way less than the sender. Yet, it must also be temporal because its effects occur in time.
The missions can be understood to be prolongations of the processions ad extra. Thus, they are connected to the origins of each Person but distinct from other ad extra actions, such as the creation. In this we can see a distinction between the order of grace and the natural order of creation. The mission implies the eternal origin of the persons and the new effect found in creation. Thus, the missions are eternal in the sense that the divine persons go forth from eternity. However, their effects are temporal because they occur in time.
Great care must be taken when speaking about the Holy Trinity because errors can be made both in denying the unity or the plurality of God. It is the case that the divine nature is one and so names that signify the divine essence substantively are predicated to the three persons singly. On the other hand, words that describe the divine essence adjectivally are predicated plurally. If we are not careful, we can accidentally express a distinction of nature or an inequality between the persons of the Trinity. At the same time, we must refrain from statements that exclude a plurality of persons such as singular or solitary.