This is not heresy, as it does not establish any ontological inferiority or ontological subordination. Jesus Christ was also a real man; thus, he could have said and done all this as a man. Under the title of the Trinitarian procession (processio, ἐκπόρευσις), the Son is in a (conceptual) dependence on the Father, and this provides sufficient logical basis for the manner of speaking that the Son follows after and is "subordinate" to the Father in the economy; moreover, the Father, as the source of the Trinity, is αὐτόθεος, and therefore it is particularly appropriate to attribute the name "God" to Him in distinction from the other two persons. This should inform our understanding of Jn 17:3 and 1 Cor 8:5–6.
Not every expression that tastes of heresy immediately contains heresy. Namely, the so often mentioned subordinate expressions most often allow for a completely correct orthodox meaning: a) From the standpoint of origin, the Father is first, the Son is second, and the Holy Spirit is third. This sequence does not imply a rank, essence, and temporal sequence within the Trinity itself; however, in human perception tied to time and in expression, it takes on a form of subordination; one who is for any reason placed later in the order, our discursive thinking and valuation are inclined to also place lower in rank; yet, one who speaks thus does not necessarily wish to deny actual essential and rank equality, or indeed teach heretical subordination. b) In the series of visible missions, the Son appeared in a later phase of salvation history, the Holy Spirit even later; whereas the Father is the eternal sender, who Himself is not sent; thus, from this perspective, it can be said that the Father is invisible, while the Son has become visible; similarly for the Holy Spirit. Therefore, if the early Church Fathers, when reasoning about the mysteries of faith, do not yet distinguish precisely between sending and manifestation, property and appropriation (proprium et appropriatum), their teaching is not heretical.
Trinitarian appropriation (appropriationes) is the appropriation of some common divine excellence, i.e., property or act, to a particular person (Thom Verit. 7, 3.). This appropriation of common divine excellences, or Trinitarian appropriation, is allowed under two conditions: a) It must not attribute a common excellence to one person in such a way as to exclude the others; i.e., the appropriation must remain an appropriation and not take on the character of a property; otherwise, it would contradict the preceding proposition. b) It must be theologically grounded; that is, it must take into account the personal properties. Appropriation is only correct if it is related to the personal properties. In this interpretation, it is the universal conviction of theologians that appropriation is not only allowed but also very beneficial.
Each divine person of the Trinity is not only the possessor but also the representative of their personal properties; thus, if we attribute related excellences to them, we also make our knowledge about them more direct, vivid, and enriched; e.g., if we attribute inventive, faithful, holy love for humanity to the Holy Spirit. Indeed, "if we always spoke of the undivided Trinity in an undivided way, we would never know it as Trinity." (Leo M. Serm. Pentec. 2, 2.) The ultimate reason for this is the limitation of our mind, which can only get a somewhat colorful and sharp picture of the divine persons of the Trinity by making each a separate object of contemplation, beyond what the Trinitarian constituting opposing relations say. The logical basis for this is given, on the one hand, in that a certain common divine property or activity in our finite consideration is more closely related to one divine personal property than another, e.g., our adopted sonship with the sonship of the eternal Word; on the other hand, in the fact that, as a result of the Incarnation, at least about the Son of God, we assert excellences that are no longer mere appropriations.
In creation, and especially within the supernatural order, divine attributes and activities gain a very distinctive color, efficacy, and life when we bring them into direct and lively contact with a divine person. This is because, on one hand, the power and warmth of the respective Trinitarian person's personal attributes also radiate upon them. It says much more: The Spirit of God (the warming, vivifying, fertilizing Spirit) hovered over the waters, than if we simply read: God was over the waters. On the other hand, through appropriation, the natural or supernatural states of being also enter into mutual relations which mimic the Trinitarian relations, and reflect the rich fertility and harmony of the Trinitarian community of life onto creation. For instance, the relationship between freedom and authority, tradition and research, is seen in a completely new light once we associate it with the Word and the Spirit through appropriation.
Therefore, it's not surprising that Scripture also makes ample use of appropriations. For example, the angel attributes the Incarnation to the Holy Spirit (Lk 1:35); Saint Paul usually attributes the name "God" to the Father, and the name "Lord" to the Son (1 Cor 12:4; cf. Rom 11). The Apostles' Creed attributes the work of creation to the Father, redemption to the Son, and sanctification to the Holy Spirit, thus integrating the pivotal facts of salvation history into the golden chain of the Trinity. The Church Fathers also widely use appropriations, and the great medieval theologians develop their system (L. Bonav. Breviloqu. 1, 6; Thom I 39, 7 8; beautiful deep appropriations concerning the Holy Spirit in Gent. IV 21 22).
The main types of Trinitarian appropriations (according to Thomas Aquinas):
1. From the perspective of divine being: According to Augustine, in the Father we see eternity (for he is without origin), in the Son beauty (the radiant image of the Father), and in the Spirit enjoyment (the seal of the holy love of the Father and Son) (August. Trinit. VI 10, 11; cf. Hilar. Trinit. II 1.). Furthermore: "In the Father shines unity, in the Son equality, and in the Holy Spirit the harmony of unity and equality. With respect to the Father, there is unity in all things, due to the Son there is equality, and due to the Holy Spirit, connection." (August. Doctrina chr. I 5.) Here, the relation to personal properties is evident: We claim unity about the thing without relation to anything else, represented by the Father, who is the principle without origin; equality is most strikingly reflected in the Son, who is the image of the Father; the Holy Spirit, as the bond of love between Father and Son, is therefore particularly suitable to represent the harmony that connects opposites.
2. From the perspective of capabilities, we attribute power to the Father (He is the source of the Trinity), wisdom to the Son (the eternal Word, into which the Father speaks, utters His thought), and goodness to the Holy Spirit (the gift of love from the Father and Son). Related appropriation: the Father as God (self-existing); the Son as Lord (through whom all things were made); the Spirit as the Giver of Life and Comforter.
3. From the perspective of activity: According to Saint Paul, "For from him and through him and for him are all things." (Rom 11,36) Here, the origin of things is put into an appropriative relation with the Trinity. That is, the Father as the source of the Trinity is most suitable to represent the founding principle and cause. The Son, as the exhaustive expression of the Father's self-knowledge, is suitable to represent the exemplar causes; furthermore, as (according to the Greek Trinitarian understanding and formulas) the mediator who leads the divine substance to the Holy Spirit, in outward activity he is also considered as the mediator (through whom all things that were made, were made). The Holy Spirit, as the completer of the Trinitarian self-giving and the seal of the love of the Father and Son, is suitable to be the personal representative of the purpose of every natural and supernatural activity. From this follow also the following frequent and productive appropriations: the Father as creator, the Son as shaper, the Spirit as completer; in the supernatural order, the Father as creator and giver of grace, the Son as the redeemer of grace, the Holy Spirit as the principle of individual sanctification; in all divine activity, the Father initiates, the Son continues, and the Spirit completes; or the Father commands, the Son executes, and the Spirit completes. Therefore, the "Son is the arm of the Father, the Holy Spirit is His finger" (the hymn's "digitus paternae dexterae" is an extraordinarily tender and expressive phrase for the entire Trinity). In worship, all prayerful and sacrificial devotion is directed to the Father, through the Son, in the Holy Spirit.
In fact, God Himself is a mystery, since the finite mind cannot comprehend the infinite God. The fact that the trinity is a mystery does not mean that what is in Revelation cannot be understood by reason. The doctrine of the Trinity summarizes the biblical data: there is only one God, but at the same time there are three persons, who by nature are what only God can be, and who do things that only God can do. God is one God in three persons: Father, Son and Holy Spirit. This is not meaningless, it is just beyond reason, unprecedented in the created world: God does not resemble human ideas (cf. Acts 17:29). 1 Cor 14:33 does not speak about the being of God, but about the need for church order (i.e. he is the God of peace).
"Mystery of faith" (mysterium fidei) in the full sense of the word: every religious truth that the mind, with its sheer natural talents, cannot either determine or understand with its specific concepts. Thus, it contains two components: The mind on its own cannot determine its existence, and even if it has gained knowledge of its existence through revelation, it is subsequently unable to justify it with purely natural reasons; moreover, it cannot define its meaning with specific, but only with analogical concepts. In other words: A mystery of faith is such a religious truth for which the mind on its own cannot determine either that the predicate "must" be asserted about the subject, or that the predicate "can" be asserted about the subject; for example, the one God is three persons; Jesus Christ is truly present in the Eucharist under the appearances of bread and wine. If either of these two components is missing, that is, if the existence of a religious truth can be recognized by reason, but its manner is not comprehensible (for example, God created the world), or its existence cannot be determined by reason, but once we learned it from revelation, its content is already accessible to reason (for example, Christ appointed a head for His Church; there are seven sacraments), then we are not dealing with a mystery of faith in the full sense of the word, a primary mystery, but only with a secondary mystery of faith.
Those who define the mystery of faith as the incomprehensible, indomitable religious truth do not define it accurately. Because there is something incomprehensible, indomitable in every human knowledge; and that is why the deeper-thinking people of every age talk a lot about the depths and mysteries of existence, and praise the docta ignorantia (Nicholas of Cusa). However, this is something entirely different from the nature of the Catholic mystery. The world of nature hides secrets because our mind does not create its realities but faces them as givens and can only perceive them fragmentarily; the mystery of faith, on the other hand, cannot be measured by reason because it is from the higher, superhuman world of realities.
The Bible uses the word "mystery" in two different senses. Generally, it tends to refer to an event or phenomenon in which God and man meet each other, and God gives Himself as a gift to man (Eph 1:9; 3:9-11; 5:32; Col 1:26). The other meaning of the mystery in the Bible is concealment and incomprehensibility (Rom 11:25; cf. 11:33-34; 1Cor 15:51; Rev 17:7). In this regard, theologians categorize the mystery of the Trinity among the so-called absolute mysteries (mysteria absoluta).
The fact that the doctrine of the Trinity is a mystery of faith in the strict sense is indicated by the Jesus himself when he says: "No one knows the Son except the Father; no one knows the Father except the Son, and those to whom the Son chooses to reveal him." (Mt 11,27.) John the Evangelist: "No one has ever seen God; the only begotten Son (the only begotten God), who is in the bosom of the Father, has revealed him." (Jn 1,18) Paul the apostle: "No one knows the things of God, except the Spirit of God." (1 Cor 2:11; cf. 1 Tim 6:16.) Since the Church Fathers Irenaeus and Origen, it has been unequivocally taught that the Trinity surpasses the mind. When the Arians boldly wanted to lift the veil that covers the inner nature of the Deity, their main weapon against their heretical position was reference to the mystery of the Trinity (Iren. II 28, 6; Origen. Princip. IV 1; Athanas. Serap. I 20; Cyril. H. Cat. 4, 7; Basil. Ep. 38, 4; Nazianz. Or. 31, 8; Nyssen. Or. cat. 3; Cyril. Al. Trinit. 3; August. Trinit. IX 1.).
But what does this mean? It cannot be determined by the mere powers of the natural mind that the one divine reality is a trinity of persons.
It's not a posteriori: for the a posteriori proof of God starts from the created world and reaches the absolute being through the thread of causality. It is already a theologically established truth that God's trinity as such is not manifested in creation; for God's external activity is the common work of the three persons: Therefore, the mind does not have a foothold in creation to recognize the one God subsisting in three persons as the absolute being.
And it's not a priori either: we cannot deduce the Trinity from the nature of God known through reason; partly because we do not know the divine reality in a proportionate way, partly because experience does not provide any analogy for a triple relative subsistence of one substance.
But even if we have come into possession of this mystery through revelation, we can neither understand nor subsequently justify it. For even if the analogy of human spiritual life suggests that God's absolute life cannot lack the richness that feeds on the contrast of spiritual activities and life contents, and even if the mind faithfully following the traces of revelation can penetrate a good way into the cloud hiding the Divinity, its laborious thought processes invariably lose their way at three landmarks in the impenetrable fog sea of the mystery:
Initially, independently of the revelation, the mind cannot determine that there are only two categories of spiritual activities and capabilities, reason and will, and hence only two origins are possible in God.
Initially, without revelation, it cannot determine and prove to be necessary that divine life activities are productive; because it is very conceivable from the outset that the object and proportional expression of divine understanding and volition is the independent infinite absolute reality, without the difference of opposing subsistent aspects.
Independently of revelation, the mind can neither determine nor judge it possible that the one divine absolute reality can be the existential content of three subsistent aspects, which are only value-differently from it, but are really different from each other.
While the Trinity is a supra-rational truth, it is not irrational, but completely rational. For the Trinity is God's self-revelation. But God is absolute reason, therefore this revelation is the radiance and evidence of absolute reason. God cannot give anything other than what is his essence. True, the Trinity is a mystery in the strict sense of the word, and therefore the human mind cannot fully demonstrate the logic that this mystery contains. But for this very reason, irrationality cannot be demonstrated from it either. The mind on its own can determine that God is immeasurably superior; this unattainability is always maintained for our mind, whether it reaches for it for understanding or for refutation.
But the mind, illuminated by revelation, can demonstrate in a negative direction that the mystery of the Trinity does not contradict clear arguments, and in a positive direction it can catch a ray of the abundance of light bursting forth from it.
The doctrine of the Trinity could only be shown to be irrational if it contradicted any logical principle, namely the principle of identity and contradiction. But this is not the case. We do not say that the same subject is one and three, but we affirm that the divine reality is one, and the persons are three; or we call the substance one and we state the subsistence as relatively three.
Indeed, the content of the mystery of the Trinity (the triple relative subsistence of one absolute reality) contradicts experience, even the metaphysical findings derived from the material of experience. But its irrationality cannot be inferred from this. For every deeper thinking person has sensed that experience does not exhaust the categories and possibilities of existence, and that is why even within this world, the mind inferring from the present to the past, from the here to the far, is cautiously warned not to hastily infer from non-existence to impossibility. This is particularly true when the mind, leaving the ground of experience beneath itself, rises toward the regions of the absolute Being, where, according to the strict requirement of natural theology, every metaphysical concept must be re-evaluated with the triple method of God-knowledge. Therefore, it cannot be said that the relatively triple subsistence of the absolute Being is irrational; the less so, because reason also determines that God is above the sexes, therefore the Aristotelian categories cannot set a limit to his existential content and mode of existence.
The mind can first and foremost pour its content into systematically processed concepts and thus speak appropriately about it; it can determine which expressions and phrases correspond to the content of the mystery and which do not.
The general rule of speaking about the Trinity is: everything in God is one, where there is no contrast of relations; therefore, if the excellence of nature is the predicate, the subject can be nature or a person; if the predicate is personal excellence, the subject can only be a person. If we now consider that the concrete noun (and the male adjective in Indo-European languages) generally denotes the autonomous reality, the suppositum, hence the person in the doctrine of the Trinity, the abstract noun (and the neuter adjective) denotes the nature, it is generally not difficult to navigate and determine the correctness or incorrectness of a phrase or expression. Thus,
a) we can say that the Father, as well as the Son and the Holy Spirit, are eternal, omnipotent, etc., but we cannot speak of three eternal or omnipotent entities.
b) It is correct: the Son is someone else (alius) than the Father, but not: the Son is something else (aliud). It's correct: the one God is in three distinct persons (in tribus personis distinctis), not correct: the one God is divided into three persons (in tribus personis distinctus), as this endangers the unity of the essence.
c) We can say: God begets, God breathes; the Son is God from God; because the concrete noun signifies the suppositum; but we can't say: divinity begets, divinity is Father. However, often the established language usage decides. The speech of the believer cannot roam freely like that of the philosopher; "our speech must be according to a definite rule, lest the liberty of speech should generate an impious belief about the thing itself". (August. Civ. Dei X 23.) If anywhere, here, in the mystery of mysteries, Paul's warning is appropriate: "O Timothy, guard what has been entrusted to you, avoiding worldly and empty chatter". (1 Tim 6:20. How much the sealed language usage of the Church decides is a telling example: the Latin Deus triplex is incorrect, but the identical etymon, dreifaltig, threefold is orthodox.)
The believing mind may attempt, in the humble consciousness of its limitations, to illuminate some aspects of the mystery of the Trinity with analogies taken from natural or supernatural life. Of course, it must not forget that in these there will always be more difference than similarity; each one is only good for casting a faint, fading light on one aspect of the mystery. The Greek church fathers used more external analogies: the sun, its light, its ray; in a tree the root, trunk, flower; plant, flower, fragrance; source, stream, estuary; three torches that are ignited from each other (perhaps better: three torches whose flames merge). The newer catechesis and speculation also refer to other analogies: the three dimensions of space, the three moments of time (past, present, future); the three moments of processes: beginning, continuation, end; the three transcendent basic properties: one, true, good; the three basic categories of causality: real, formal and goal-cause (with the last two in relation to the three proofs of God the onto-, nomo-, teleological). The most fruitful analogy, however, is human spiritual life. The Greeks also stayed more on the surface here, as they associated the second divine person, the Word, with the spoken word, the Holy Spirit with the breath. The brilliant mind of Augustine reached the root of spiritual existence, and there he found the purest mirror image of the Trinitarian origins: "The Trinity gives a certain image of itself in the intellect and in the knowledge, which is the offspring of the intellect: the word it says about itself; thirdly, love; and these three are one substance. And the Begotten One is not less, for the intellect knows itself as much as its existence is; and love is not less, for it loves itself as much as it knows itself, and as much as it exists". (August. Trinit. IX 12, 18.)
If we consider any of the aspects that make up the mystery of the Trinity as given from the revelation, we can almost unravel the rest along its thread; a clear sign of how powerful logic prevails in all the relations of the Trinity. For example, if we take this truth as given: there are two fertile origins in God, we can deduce that these origins are immanent, eternal, and substantial, that their product can only be a person and there can only be three persons, two of whom generate the third as one principle.
Finally, the believing mind can reveal the philosophical, theological, and religious significance of the mystery of the Trinity.