The Unified oneness of God
Trinity: Oneness in unity not in number: Yachid vs. Echad
No one talks about three Gods. The fact that, along with the Bible, we refer to three different persons as God does not equate to the statement that there are three Gods. Because these persons are not three different Gods since their Godhood, their essence, is one and the same. The Trinity pertains only to the divine persons, not to the one divine essence; that is, there is only one God. What is one in God, we call the divine essence or nature; what is three in God, we call person or subject. Therefore, God is three persons in one essence, while Jesus Christ is a single (divine) person in two (divine and human) natures. The multiplicity of persons can in no way be contrasted with the unity of essence, although it is true that without revelation, we would have no idea that "personality" and "essence" do not always coincide. The fact that the two coincide in humans does not mean that the two concepts are the same thing. There would only be a conceptual contradiction if we were to say: one essence and yet three essences; one person and yet three persons. But: one essence and three persons is no more a contradiction than saying three men and one family, or a hundred soldiers and one company. We do not identify the three with the one, but the three divine persons with the one God. It is not possible to demonstrate a conceptual contradiction in this.
Deuteronomy 6:4 says, "Yahweh is our God, Yahweh is one!" In the Bible, Yahweh is "one God" in the sense that there is no other: the only one. Therefore, the text does not claim that God, in terms of His being, is one person, but that there is only one God. How many persons exist is another question. Monotheism is the common confession of faith of Israel (Deut 4:39, 6:4, Isa 43:10) and the Trinitarian apostles (1Tim 2:5, James 2:19). The phrase "God is one" is a poor, literal translation of 'heis ho theos'. The meaning of the Greek elliptical sentence without a verb is this: there is one God - and not many, so this passage only contrasts with polytheism, not with the monotheistic doctrine of the Trinity. The masculine form of the Greek numeral (heis, mia, hen) refers to the singularity of a person; if the neuter 'hen' were used instead, it would imply some kind of unity or oneness.
The summary of the mystery of the Trinity: The one God is a Trinity, Deus unus Trinitas. Since it is impossible to affirm unity and trinity about the same subject without contradiction, the question arises: in God, what should be said to be one and what three. According to the teaching of the Fourth Lateran Council, in God, there are three persons or hypostases, and one essence, substance, or nature.
Therefore, in God, there is one essence, the totality of the divine being, what is sometimes called God's physical essence. The substance, which in theological language is often and in philosophy generally is what stands under (quod substat), as opposed to accidents: that which exists in itself and not in another as in an internal subject (ens existens in se et non in alio tamquam subiecto intrinsecae inhaesionis). However, in theological language and always in Trinitarian doctrine, it means the existing essence of a hypostasis. The nature, that is, the complete being from the perspective of activity; what is essentially static, dynamically considered as nature, the indirect principle of activities (principium quo agendi remotum).
In God, there are three: 1. The hypostasis (suppositum = the personal, independent being), that is, the complete, independent hypostasis, which not only exists by itself, as substance generally does, but also possesses its own, insofar as it is not attached to anything else as a physical or essential part (e.g., the arm to the human, the soul to the body). The complete hypostasis is characterized by its complete being in its kind and by its incommunicability. The complete, independent hypostasis forms a closed circle of being and activity; entirely unto itself, and in this sense, the possessor and subject of its activities (principium quod agendi): actions are of the suppositum. 2. Subsistence in the concrete sense is identical to the suppositum; in the abstract sense, it is the mode of being of the suppositum, or the complete, independent hypostasis. Thus, the suppositum subsists = the hypostasis exists independently. 3. The person is a rational hypostasis, that is, a being whose closed independence and personal existence consist in (at least potentially) holding itself through the power of its own consciousness and will: conscious and self-powered, having rights over itself (sui iuris). This is also articulated by Boethius's famous definition: persona est rationalis naturae individua substantia. Therefore, a person is an individual who, in terms of its mode of being, is hypostatic, and in terms of its being, is rational (actual consciousness is not a part of the concept of person!).
Although the content of these expressions was professed by the fathers from the beginning, insofar as they spoke of the one divine reality as Father, Son, and Holy Spirit, the expressions themselves were not initially fixed unambiguously and only gained their precisely outlined meaning after centuries of fluctuation. Thanks to the linguistic genius of Tertullian and his unmatched authority, the Latin usage settled sooner in this development.
Among the Greeks, there was never any discrepancy that what is one in God was called φύσις. But already οὺσία was taken by many in the spirit of Platonic philosophy to be identical with ὑπόστασις, and thus with Origen, they professed ἑτεροουσία about the Father and the Son; the Council of Antioch in 269 also read monarchianism into Paul of Samosata's ὁμοούσιος. The Latins hesitated for a long time to use hypostasis, which in a literal translation means substantia, because since Tertullian, the Latin Church had used substantia to indicate what is one in God. Even in 362, a Council in Alexandria had no objection to someone professing one hypostasis or three consubstantial hypostases about the Trinity. However, the Greeks long struggled with persona, because the corresponding Greek word πρόσωπον also means actor's mask, role, appearance, and in this sense, it was also misused by Sabellianism. Basil significantly contributed to making Greek Trinitarian terminology more precise. Since then, the Greeks' preferred formula is: μία οὺσία ἐν τρίσιν ὑποσπάσεσιν.
The believing mind transfers these expressions to the Trinity, just as it does other concepts, not analogically or metaphorically, but in their proper sense, and teaches: The one divine reality or nature, that is, Being from itself, subsists in three persons; that is, the one divine essence is the completely identical possession of three persons. We prove this from the sources of revelation. The relationship between the three persons and the divine reality is such that the divine reality and the three persons differ only in value, not in actual difference (virtualiter, non realiter); the Father, Son, and Holy Spirit differ from each other actually (realiter metaphysice), namely, in that the Son is eternally begotten of the Father, and the Holy Spirit proceeds eternally from the Father and/through the Son.
The persons of the Trinity are relative (relational) persons. This means: each of the three persons must only be thought of in relation to the other two; the Father is a person only by begetting the Son and breathing the Spirit; the Son is a person only by being begotten from the Father and breathing the Spirit; the Holy Spirit is a person only by being breathed forth from the Father and the Son. If one were to stop thinking at the Father or the Son, it would create the illusion as if a Trinitarian person could be considered in isolation; which would only be possible if one did not place the defining characteristic of Trinitarian personhood in the subsisting relation; and this, in turn, could only be conceptualized in the form of Sabellianism or Tritheism.
From this, it follows that the definition of the divine person must include, as an essential feature alongside the incommunicable complete autonomy, the being-for-others: the Trinitarian persons exist for each other. The personal reality of a created person does not signify isolation and shrinkage. Each human being is created by God to live in community, from community, and for community, and in this way, their being is essentially complemented; but primarily so that they may live for God, thereby ensuring the only worthy content of life for the person, the eternal truth. However, this openness for others is rooted in their finitude, and its realization, the community of persons, can at most extend to a community of feelings, thoughts, and interests; there is no way (within the order of nature) for two persons, however close they may be, to transfer their substance to one another. In the Trinity, the relativity of the persons means precisely this: The Father pours His entire substance into the eternal Word, the Father and the Son breathe their entire being into the Holy Spirit. The life community of the Trinity is so intimate that it surpasses all measure, and gives a hint of why the Church so often utters this prayer: "O beata Trinitas!" (Oh, blessed Trinity!), and what it means for the hope prefigured in sanctifying grace: eternal participation in the life community of the Trinity.
The perichoresis (mutual indwelling) of the Trinity: The persons of the Trinity fully permeate each other and are in each other. This is a doctrine of faith. The Council of Florence solemnly declares: "In God, all is one, where there is no opposition of relations (in Deo omnia sunt unum, ubi non obviat relationum oppositio). Because of this unity, the Father is entirely in the Son and entirely in the Holy Spirit, the Son is entirely in the Father and in the Holy Spirit, the Holy Spirit is entirely in the Father and entirely in the Son." This mutual full reality-community is called περιχώρησις by the Greek Church, which means mutual indwelling, interpenetration, circumincession: the persons mutually permeate each other, each with the full content of their reality passing into the other; in Latin, it is more often referred to as circuminsessio, being-contained-in-each-other, reality-in-each-other: the persons, with the full content of their reality, rest in each other.
