In the Word of God and in the Church tradition, the personal nature of the Divine is firmly established. God the Father speaks of Himself: I, God the Son speaks of Himself: I, and of the Comforter Spirit: He. The whole Holy Trinity in Unity speaks of itself: I and We. This personalism of the revealed doctrine of God, which is pre-emptive of the impersonal conception, is the basis of the patristic teaching on the Holy Trinity, which attempts to express the dogma in the language of religious philosophy, in metaphysical terms, to formulate a logical concept.

The nature of the spirit. God is a Spirit (Jhn 4:24). The nature of any spirit consists in the inseparable combination of self-consciousness and originality, or self-foundation, hypostasis (ύπόστασις, persona) and nature (φὐσις, natura). Outside of self-consciousness, the spirit does not exist, every spiritual being is conscious of itself as I, is I (from this primary immediacy, the indefinability of the I is also clear). This I, uniting in a mysterious and indescribable way with its basis, is the image of being, the revelation of this nature or that which, not itself being a hypostasis, is hypostasized in the I, becomes a living soul. The I has its own depth into which it casts its light, and in this relationship between the I and the nature of the I, the life of the spirit is realized as a self-founded, self-founded self-consciousness. It (I) exists in an absolute way, having on itself in this respect the image and seal of the Absolute Spirit.

The I is insoluble, but it is also indefinable. Any attempts to define or describe the I (as aseitas or perseitas, integritas, independentia) concern certain aspects of the special experience of the I, personal self-consciousness, which can only be named, indicated by a verbal gesture (pronoun). The I is indefinable, because it is absolute, everything exists in it, in the rays of its sun, which is the source of light and shadows, shapes and colors, but therefore cannot be determined by them. Self-consciousness of the I is therefore unprovable, but only demonstrable. I am I, and nothing else, it looks into itself, defines itself. It is not subject to time, because above time, it knows neither origin nor death, it remains eternally. Every human I is, in a certain sense, supremely peaceful and absolutely: it is the eye of eternity, through which only one can see time, in it there is an eternal day and no immersion in nirvana. (And the states of sleep and unconsciousness interrupt the empirical self-consciousness, but do not introduce any break in the self-identity of the I.) I have everything in myself and for myself (if not available, then in the possibility).

The nature of the spirit. … It (I) exists in an absolute way, having on itself in this respect the image and seal of the Absolute Spirit. But it also bears the stamp of its non-absoluteness, or creatureliness, having its own border, and this border is the monohypostatizedness of the spirit. Any I is limited, because it inevitably turns into you or we, i.e. to other I [ … ], and cannot be unaware of the possibility, and, consequently, the inevitability of such a way out. The attempt of the I to lock itself in Luciferically, loving oneself with absolute love, makes him only a victim of this limitation of his, affirmed as absoluteness (Fichteanism). The boundary I is vitally removed in love, where I is preserved, destroying itself, going beyond its limits to another I, and then it becomes the image of the Absolute Spirit in relation to his hypostatic existence. The absoluteness of the hypostasis is resolutely opposed by the limitedness of I, taken in the singular, it requires going beyond this line. But in the created nature, this limitedness is only reaffirmed by this exit, for here, next to one I, other I are placed, absolute centers multiply, and this multiplicity testifies to their relativity. This could be absent only in that one case, if the exit to another I is not an exit beyond the limits of its being, but remains inside it, therefore, it will take place not in the single-hypostatic, but in the not-single-hypostatic spirit. According to Christian revelation, God is a trinitarian spirit, having three faces and one being, the One in the Trinity and the Trinity in the One: “The One, moving from the beginning to the two, stopped at the Trinity” (St. Gregory of Nazianzus). The absolute mono-hypostatic, having itself and everything in an unconditional way, would be not only a contradictio in adjecto, but also an expression of metaphysical egoism, absolute limitation, Satanism. But if the postulate of the not-mono-hypostatizedness of the Absolute Spirit is also accessible to the limited spirit, then the secret of this non-mono-hypostatizedness of the Absolute Spirit cannot be revealed by him in the implementation, it becomes the subject of a frank teaching about the Holy Trinity, which, to a degree accessible to the created consciousness, brings it closer to its comprehension.

At the basis of self-consciousness, as well as any act of thought that captures it, lies the trinity of moments, the trinity, which is expressed in a simple proposition: I am A. Generalizing this in logical-grammatical terms: subject, predicate and connective, one can say, that the basis of self-consciousness is the sentence. The spirit is a living, unceasingly self-realizing sentence. … Each sentence can be reduced to the type of connection of the I with its predicate, it can even be said that, having a true subject of the I, it is, in its entirety, the predicate of this I, because in relation to the I, everything, the whole meaning is a predicate. And each assertion is a new and new self-determination of the I, if not in form, then in essence. Each assertion is ontologically brought to the general relation of subject and object, which are nothing but I, hypostasis, and its nature, revealing its content, its predicate, it is also brought into connection with the subject connective of being. … I, self-closed, located on an inaccessible island, to which no thinking or being reaches, finds in itself a certain image of being, expresses itself in the "predicate" and cognizes this image as its own creation, self-disclosure, which is the connective. In this sense, our whole life, and therefore all our thinking, is a continuously realized sentence, it is a sentence consisting of a subject, a predicate and a connective. …

… Hypostasis, person, I, exists, having its own nature, i.e., its revelation, which is constantly said and never completely uttered, which it realizes as its own being (in its various shades or modalities). …

The hypostatic I is indefinable in its very essence. Being I, the hypostasis, everyone knows what is this about, although it is inexpressible (but only utterable). It is the very essence of hypostasis that it is indefinable, indescribable, stands outside the word and concept, and therefore cannot be expressed in them, although it is constantly revealed in them. Before the face of the Hypostasis, silence is appropriate, only a mute mystical gesture is possible, which is not called by a secondary, reflective act, but “instead of a name” is denoted by a “pronoun”, I [Булгаков С.Н., Философия имени]. … For the I, the hypostasis, is truly a thing-in-itself, a noumenon, and it, that is, the spirit itself, forever remains transcendent to thought in its nature, position, and relation to it. But the transcendent is always and inextricably linked with the immanent, immanentized; the subject, the hypostasis, is always revealed, expressed in the predicate. It goes without saying that the hypostasis in this sense is not a psychological I, psychological subjectivity, which is already a determination of the hypostasis, a predicate, not a subject: the spirit is not psychological, and the hypostasis is in no sense psychologism. … For hypostasis there is no rise and fall, no beginning or end. Timeless, at the same time it is supertemporal, eternity belongs to it, it is eternal in the same way and in the same sense as God is eternal, who Himself breathed His Spirit out of Himself into man at his creation. Man is the son of God and the created god, and the image of eternity is inherent in him inalienably and inseparably. Therefore, a person can neither conceive nor wish for his own destruction, i.e., the quenching of I. (and all suicide attempts are a kind of philosophical misunderstanding and do not refer to the I itself, but only to the mode of its existence, not to the subject, but to the predicate). The hypostatic I is the Subject, Subject to all predicates, its life is this predicate, infinite in both breadth and depth.

… it is necessary to set forth the following trinitarian axiom: The Holy Trinity is a divine triunity which is exhaustive and perfect in Its fullness, a triunity of interrelations which is trine and integral in all Its definitions, without any disjunctive or conjunctive "and" connecting the separate hypostases. Every hypostasis in separation, as well as their triunity, must be understood in trine connection and in trine self-definition, which form the Whole, the Holy Trinity.

But besides this there is also the triune nature of the consubstantial Trinity, which is substantially identical with the nature of each of the individual hypostases, while differing from this nature modally, as it were, according to the mode of its hypostatic possession. This difference refers, of course, not to its ousian essence but to the mode of its possession by the Holy Trinity in the triunity and by each individual hypostasis.

The Holy Trinity is the trinitarian act of the self-definition of the hypostases; and each of the elements of this trinitarity, despite the aseity and equi-divinity of the three hyposcases, is correlative to the other two hypostases and in this sense is conditioned by them. The fullness of natural being, as self-revelation, is given only in the trinitarity of the hypostatic self-definitions. Naturally too, the Holy Trinity exists only trinely, «consubstantially and indivisibly», which is why each of the individual hypostatic modes of natural being does not simply exist, but coexists in its indivisibility with the others. Therefore, in general, none of the hypostases in its separate personal being can be understood except in trinitarian conjugacy. This leads to a general thesis, which is a kind of axiom concerning the Holy Trinity: the three hypostases, in their character, are not single and not double, but trine. They must be understood not on the basis of themselves alone, but on the basis of their trinitarian union; they are defined and shine noc only wich their own lighc, but also with the light reflected from the other hypostases. It follows that all three hypostases must be understood in a distinctly personal as well as trinitarian manner; and any doctrine that transforms the Holy Trinity into a system of originations and dyads is fundamentally deficient.

With the victory of Orthodoxy, homoousianism, faith in the trihypostatic God, over the doctrine of the monoadic monohypostaciety of the Godhead, the whole formulation of the question about the relations of God anf the world is changed. It is now impossible to say about the trihypostatic God that which inescapably has to be said about the monohypostatic monad that needs the world: the life of the trihypostatic Godhead as Love, as preeternal mutuality and self-revelation is absolutely self-sufficient and complete, it needs no one and nothing and cannot have any supplementing. The trihypostatic God lives in Himself, i.e., in the Holy Trinity, and this Life is a pre-eternally realizing Fulness. Hence the world is not necessary for God himself and it is powerless to add any supplementing to the Fullness. The world is entirely a creation of the generous and magnanimous love of God, a love which gives and which receives nothing. God is necessary for the world as its foundation and goal, but not the reverse. By trihypostaseity the solitude of the Absolute subject, his aloneness, is overcome, and thanks to this victory the monohypostatic God is compelled as it were to create the world. The Trihypostatic God is one in His triunity, but not alone…

God is Love (I John 4:8) as a trinity in which the eternal act of reciprocity and self-giving in love is carried out. The One Absolute Subject reveals this absoluteness of its own in the act of mutual love of the Three, thereby overcoming the limitations of the self, going out into the other self through self-giving and self-exhaustion in sacrificial love, and in it regaining this given self, so that the three hypostases in their unity are the realization, the revelation of the one absolute Self. As an Absolute subject, a trinitarian existing Self, God speaks of Himself: I am that I am (Exodus 3:14), I am the Lord thy God (Exodus 20:2, 5, etc.). As a trinitarian existent subject, God speaks of himself: Let us make man in Our image (Gen. 1:26); Behold, Adam became like one of Us (Gen. 3:22). Also, about the appearance of God in the form of three men to Abraham it is said: and the Lord appeared to him... and said (to Abraham the three): Master! (Gen. 18:1, 3). Each hypostasis is the true God, existing through other hypostases, inseparable from it, having one common nature, neither merging nor dividing, so that there are not three Gods, but Unity in Trinity and Trinity in Unity, a single trinitarian subject. In the difference of hypostases, as having absolute significance, the secret of intra-trinity life is revealed by their quality: with the unity of their nature and their equivalence, there is an ontological relationship between them: the first, second, third hypostasis — the Father, the primary culprit, primary, original hypostasis, revealing itself in the second, in the Son, and proceeding from Himself to the Son in the Holy Spirit. But the one who opens, the one who reveals, and the one who unites them are equally honest in the unity of their nature and in mutual love. The Father, the imprecise beginning, the first will, gives birth to the Only Begotten Son, His Word, transmits everything (Matthew 11:27; John 3:35) to Him, but the Son wants to be a revelation of the Father, doing His will: I and the Father are one, the Father in Me and I am in Him (John 10:30, 38). But the love of two does not yet realize the absoluteness of the Subject, for it does not close its ring. Giving birth to the Son, the Father proceeds to Him with love in the life-giving Spirit, and the Spirit, as the living hypostatic love of the Two among themselves, closes the reciprocity of love in the trinity, through which the revelation of the nature of the Absolute subject, the discovery of the nature and power of I through you and in we is realized: I as the triune We, in which each hypostasis is revealed through the other, I through you and into we. In three hypostases, the Absolute subject is revealed as the Living God, for love in the depths of the Subject itself is life in itself, which the monohypostatic spirit does not know. The Trinitarian spirit is incomprehensible to him. The life of the Trinitarian Deity is a mystery for every creation, angels and men, to which there is no approach within the limits of selfish monohypostasis.

… the one life, or the one nature, of the Godhead is wholly permeated by its tri-hypostatic character; thus, while remaining one, it is threefold in its mode of being, and the hypostases themselves are the modes (tropoi, τρόποι) of the one divine life. This point must be emphatically stressed, since rationalism, in its effort to evade discursively the incomprehensibility of the dogma, simplifies and distorts it, without thereby rendering it intelligible.
One widespread exposition of the dogma asserts that the contradiction between triunity and unity is resolved very simply: triunity pertains to the hypostases, unity to the nature; consequently, in different respects God is triune and one, and thus everything becomes rationally transparent. In this view, the Trinity is likened to a joint-stock company of three persons jointly owning a certain property—that is, pure homoiousianism is preached under the guise of homoousianism (or tritheism, if the emphasis shifts toward threeness; or Sabellianism, if it shifts toward unity).
Regrettably, such reasoning can also be encountered in Orthodox dogmatics. For example: “The principal difficulty here appears to consist in how one may think of God as both one and triune at the same time. The ancient teachers of the Church did not conceal such difficulties from themselves; yet they did not consider it appropriate to suppose any contradiction here. Why? Because they knew very well that the Christian doctrine of the triune God does not require us to think God as one and triune in the same respect, but requires us to think Him as one in one respect and triune in another—namely, one with respect to the Godhead, and triune with respect to the three who exist in God: the Father, the Son, and the Holy Spirit” (Bishop Sylvester, Essay in Orthodox Dogmatic Theology, vol. II, Kiev, 1888, p. 589).
A similar rationalistic presentation is found in Macarius (Orthodox Dogmatic Theology, vol. I, p. 204): “Christianity teaches that God is one and at the same time triune, not in the same respect but in different respects: one in essence, triune in persons; one concept is given to us of the divine essence, another of the divine persons, and these concepts do not in the least exclude one another. Where, then, is the contradiction? If Christianity taught that God is both one in essence and triune in essence, or that there are both a Trinity and a single person in Him, or that person and essence are identical, then indeed there would be a contradiction.”
In both cases, the real triunity of the Godhead—both in personal being and in nature—is entirely overlooked and replaced by a mere union, or rather a community, of Three.