One of the great threats to the orthodox doctrine of God comes from those who would identify subordination amongst the persons of the Trinity. Typically the Father would be placed first followed by the Son and then the Holy Spirit in an order of dignity or of power or even of temporal existence. This position is in marked contrast to the creedal faith of the Church which insists on the co-equality of the persons of the Trinity but which allows for a certain sort of ordering in the Trinity (see Ia q.27 a.2 et passim) associated with the idea of being a principle. In this question Aquinas concentrates on rebutting these erroneous positions whilst bolstering the orthodox doctrine.
The Thread of the Argument
A1: We are probably used to an informal idea that the divine persons are co-equal, but what does it mean to say that two divine persons are equal? When we think about material things, we tend to think in terms of equality of quantity or of quality; there is some attribute of the things concerned about which we claim equality or inequality. When we think mathematically, we can put forward some absolute notions of equality as when we say that two sides of an equation are equal. When we think about the divine substance and the persons of the Trinity, we have to be careful to specify what we really mean. Aquinas starts his treatment of equality in the Godhead from the point of view of a negation of “greater than” and “less than”. The only thing there is in the Godhead to which we might apply the idea of such inequalities is the divine substance; this clearly cannot be unequal among the divine persons as they are each individually fully God. Hence we must consider the divine persons equal in this sense.
One might be concerned that with a notion of equality based purely on essence, there is nothing left upon which to base any distinction between the persons! We certainly do not believe that the Father is identical to the Son, but is this not implied by saying that they are equal? Aquinas answers that, as far as talking about God is concerned, we can signify equality (and likeness) with either names or with verbs. When thinking in terms of names, we identify the essence of the Father with that of the Son and there is a sort of convertibility between equality and likeness (a property not shared with created things). When we think in terms of verbs, there is a sort of reception by the Son from the Father of the divine essence: this allows us to say that the Son is made equal to the Father, but the Father is not equal to the Son.
Similarly we might have the concern that equality is a relation and it is by relations that the persons of the Godhead are made distinct. However, we recall from our discussion of relations in general that Aquinas does not consider equality to be a real relation but only a relation of reason. These relations of reason do not compromise the real relations that distinguish the persons.
A2: A fundamental creedal belief of Christianity is the co-eternality of the persons of the Trinity. Aquinas defends this belief with a discussion of the relationship between agents and action. He identifies that voluntary agents choose the time of their action and that natural agents produce their action when they have the power to produce the action. We might think of a natural and voluntary agent like a man as having to accrue the necessary power after which time it is down to his power of choice as to when he acts. When we think about actions, we tend to consider actions that have successive stages (they start to happen, they continue and then they cease). In this case, we cannot think of the effect as existing until the action is complete. When we consider God, we realize that He generates the Son because of His nature rather than as an act of His will and that He has the necessary power of generation from eternity. We also recognize that the generation of the Son is not a successive action (otherwise the generation would be a change in the Godhead, contradicting divine immutability). Put together, these imply the Son is eternally generated from the Father. A similar argument proves that the Spirit is co-eternal with the Father and the Son.
As one might expect, the major target of this question is the Arian heresy. The first objection is based on the Arian identification of the possible modes of generation that might be applied to the Son. Aquinas sweeps this objection aside by noting that there is no mode of procession amongst creatures that perfectly captures the generation of the Son by the Father and that the modes put forward by the Arians do not include the one that most nearly approaches the Son’s generation. This is the procession of a word from an intellect; as the intellect of God is pure act, thus not having to pass from potentiality to actuality, the procession of the word from the divine intellect is co-eternal with the divine intellect.
A further objection put forward is that if the Son is being generated eternally from the Father, this might seem to imply that the Son’s generation is not yet complete (and will never be complete). This would seem to imply that the Son lacks the perfection of having His generation completed. However, we have to remember that God exists in eternity rather than in time; there is no temporal now in which the generation of the Son is taking place; but rather an indivisible analogy of now that always abides. In a sense, one is justified in saying that the Son is eternally being born as well as that He is always already born.
A3: We’ve seen above that the divine persons are equal in terms of essence as well as co-eternal. Does this imply that we can’t identify some sort of “natural ordering” amongst the divine persons? As the Athanasian creed implies, we must never “divide the substance” or “confuse the persons”, but the lack of an ordering in the Trinity might seem to confuse the persons. Aquinas rescues the situation by appeal to the idea of “principle”. We saw in Ia q.33 a.1 that there is a “principle” in God with respect to origin that does not introduce any notion of priority. It’s on the basis of origin that we may rightly associate a natural ordering in the Trinity. Aquinas quotes St. Augustine as making the distinction that this is not “an ordering whereby one is prior to another, but whereby on is from another”.
A4: Examples from scripture (such as John 14:28, “The Father is greater than I”) strongly suggest that the Son is in some way less than the Father. Similarly, paternity is associated with the Father but not with the Son. Although Aquinas has already asserted equality amongst the persons, there still seems a lingering doubt that the Father is greater than the Son in some way. This is the challenge that various subordinationist heresies presented to the orthodox doctrine of the co-equality of the divine persons.
Aquinas’s defence of the orthodox position returns to the theme already suggested in a.1; God’s greatness is the perfection of the divine nature and this greatness is associated with the divine essence. Part of the perfection of the divine nature involves the paternity of the Father and the filiation of the Son and it is through the filiation that the Son attains to the perfection of the nature that is in the Father. Divine paternity and filiation provide an analogy with human paternity and filiation; but the analogy cannot be pushed too far as human paternity and filiation involve successiveness (see a.2). Paternity is of the essence of the Father because that is what constitutes the Father as Father; similarly filiation is of the essence of the Son. Therefore we can rightly claim that the same essence that is the paternity in the Father is the filiation in the Son and consequently the Son has the same dignity as the Father.
When we consider the scriptural witness, we can also observe the words of the Apostle Paul that “He thought it not robbery to be equal with God” (Philippians 2:6). It is clear that scripture that teaches any notion of non-equality actually refers to the humanity of Christ in the hypostatic union.
A5: John 14:10 tells us that the Son is in the Father and that the Father is in the Son; what does this mean? If we think of “being in” in the way that Aristotle took it to apply to created reality we seem to be left befuddled; it doesn’t work. Similarly, how can relational opposites “be in” each other?
Aquinas claims that the Father and the Son are “in” each other in three ways corresponding to essence, relation and origin. As far as essence is concerned, the Father is His own essence which is the same as the essence of the Son. If we think about the relation between the Father and the Son then it is clear that, conceptually speaking, the Father is in the Son is the same sense that the relation is in the Son and vice versa. As the procession of the Son is immanent to the Father, we also see that the Son remains within the Father. Conversely, everything is said by the Word and thus the Father is in the Son.
A6: Rounding off his survey of the equality amongst the divine persons, Aquinas turns to the power of Father in comparison to that of the Son. Following the strategy of a.4, Aquinas notes that power is associated with the perfection of the nature of God which is therefore associated with greatness.
A tricky objection suggests that the power of the Father enables Him to generate a Son equal to Himself, but that the Son cannot do likewise. Aquinas’ answer again alludes to the approach in a.4. Just as it is the same essence that is the paternity in the Father and the filiation in the son, so it is the same power by which the Father generates and the Son is generated. Although the power is the same, the Son is not able to generate because this omnipotence comes with a relation that differs between Father and Son.
- The starting point for understanding the equality amongst the persons of the Trinity is a recognition that ideas of equality and inequality pertain to the persons as they are the divine essence. Having grasped this, the co-equality of the persons follows naturally as does their equality in terms of power.
- The persons of the Trinity are co-eternal.
- The natural ordering of the persons in the Trinity does not imply any ordering of priority.
- Scriptural references to the Father being greater than the Son refer to the human nature in the hypostatic union.