The question has been debated whether such terms as are not found in Scripture may be used when a doctrine of the Christian religion is presented or taught, e. g., the doctrine of the Holy Trinity. In reply to this question we say that all terms which express the clear doctrine of God as revealed in Scripture should be used without fear, especially those in which the Christian Church defends the divine truth against error. Furthermore, it must be affirmed that all who believe as the Church does should also speak as the Church. Those who needlessly or frivously invent new terms not only confuse the Church by new and unaccustomed expressions, but also expose themselves to the suspicion that they seek their own glory and endeavor to introduce new and erroneous doctrines. Hence the use of new terms in the doctrine of the Holy Trinity must be discouraged.
Against Monarchianism, on the one hand, and Tritheism, on the other, the Christian Church teaches that there are three Persons in one essence (tres personae in una essentia, τρεῖς ὑποστάσεις καὶ μία οὐσία). Against Arianism, in particular, which affirmed that the l6yo; is a creature of God (κτίσις, ποίημα), the Nicene Council declared that the Son is "of one substance" with the Father (ὁμοούσιος, coessentialis, consubstantialis). The meaning of these terms is not that the Son is of like essence with the Father (ὁμοούσιος, unius essentiae specie), but that the one and same essence, which exists but once in God, is alike that of the Father and of the Son (unius essentiae numero), so that the Son is "God of God" and "very God of very God." This doctrine is truly Scriptural, John 10, 30.
The word essence (οὐσία, essentia), used of God, signifies the divine nature with all its attributes, which exists but once (singularis) in the Three Persons (una numero essentia). "By the term essence, or οὐσία, is meant the divine nature as it is in itself, all of which, with its attributes, is most simply one and singular, and thus also of the Three Persons the essence is only one." (Baier.) The term essence is therefore applied to God in a unique sense. When we apply it to men, namely, to denote something which is common to all men, the word is used as a generic term (nomen universals) or as an abstract noun (nomen abstractum), which denotes something that does not exist concretely, but is merely abstracted from the concretely existing human beings. (Ex.: It is the essence of man to think or to will.) However, when we speak of the divine essence which is common to the Father, Son, and Holy Ghost, the term essence is neither generic nor abstract, but concrete (nomen concretum), denoting something that exists actually and concretely and belongs to the three divine Persons as one in number (numero). In other words, the term essence denotes God Himself as He divinely exists as One in Three. "The essence of God is God's spiritual and independent nature, common to the three divine Persons." (Hollaz.)
By the term person (persona, ὑπόστασις) we understand in the realm of human thought an individual and rational being existing by itself (suppositum intelligens). · Thus all men and angels are persons. But also this term, when used of God, is applied in a unique sense; for when we say that the Father, Son, and Holy Ghost are three persons (personae, ὑποστάσεις, πρόσωπα), we, on the one hand, reject the erroneous opinion that there are three qualities or energies (Potenzen) and affirm that they are three rational individuals; yet, on the other hand, we deny that the Three Persons are three distinct essences, or three distinct Gods, and affirm that, while they are three rational individuals, so that the Father is not the Son nor the Son the Holy Ghost, nevertheless, the Three Persons have only one and the same divine essence in number (una numero essentia) and exert only one and the same power ad extra (una numero potentia). Hence, while the Three Persons are distinguished from one another not merely notionally (notionaliter), but really (real iter), they are in essence numerically one. When we speak of men, the axiom applies: As many persons, so many essences (Quot personae, tot essentiae); but when we speak of God this axiom does not apply, since there are three distinct divine Persons, and yet there is only one divine Essence, or God.
With respect to the term Trinity, Luther admitted that it does not "sound well so to call God"; but he adds that, since the article of the Holy Trinity is so far beyond our human mind and language, God must pardon us if we stammer and prattle about it as well as we can, provided only that our faith is pure and right; for the term Trinity merely expresses the truth that God is three in person and one in divine essence. From this it is clear that the term Trinity, just as the other terms used in explaining the doctrine of God, has not been coined to satisfy reason, but only to express the doctrine of Scripture concerning the true God. Human reason, when judging the Christian doctrine of God, must choose either between Unitarianism or Tritheism; in other words, it must either deny the three divine Persons (Monarchianism) or the one divine essence (Tritheism; Subordinationism). For this reason the Christian theologian must a priori desist from presenting the doctrine of the Holy Trinity in such a way as to make it comprehensible to reason. Every attempt of this kind involves either a self-deception, i. e., the supposition that things have been explained which cannot be explained, or a surrender of the Christian doctrine of God. Nevertheless, though the doctrine of the Holy Trinity is beyond reason, it is not against reason or self-contradictory, since Unity is not predicated of God in the same relation as Trinity. A real contradiction would exist only if the Christian doctrine would affirm: "There is one essence, and there are three essences; there is one person, and there are three persons." However, the Christian doctrine of God is: "There is one divine essence, and there are three divine Persons."
With respect to the relation of the Three Persons to one another the Christian Church teaches as follows : The real distinction of the Persons (realis distinctio, non tantum notionalis) is based upon the facts that the Father from eternity has generated the Son, John 1, 14, while the Father and the Son have spirated the Holy Spirit, John 14,26; 15, 26.
These divine acts of generation and spiration are called personal acts (actus personales) because they are not common to the Three Persons, but belong to, and distinguish, the individual Persons in the Godhead. To the Father, Holy Scripture ascribes the act of generation, John 1, 14, by which He communicated to the Son the fulness of the Godhead, or the entire divine essence, Col. 2. 3. 9. Hence the Father possesses the divine essence unbegotten (ἀγεννηθῶς), while the Son possesses it begotten (γεννηθῶς).
Scripture, moreover, affirms that the Father and the Son have spirated the Holy Ghost, Matt. 10, 20; Gal. 4, 6; for just as the Second Person is called the Son of the Father, so the Third Person is called the Spirit of the Father and of the Son. Through the spiration the Holy Ghost received the entire divine essence, Matt. 28, 19; Acts 5, 3. 4, so that He is from eternity true God with the Father and the Son.
On the basis of the personal acts, or the opera ad intra (generation and spiration), we distinguish the notiones personales of the Three Persons: the ἀγεννησια innascibilitas) of the Father, the γεννησία (nascibilitas) of the Son, and the ἐκπόρευσις (processio, spiratio passiva) of the Holy Ghost, and also the proprietat" persoooles: the paternity (paternitas) of the Father, the sonship (filiatio) of the Son, and the procession (processio) of the Holy Ghost. By personal properties we mean those peculiarities which one Person of the Godhead possesses in relation to one of the other Persons or to both, and by personal notations we mean the marks by which in general one Person can be recognized as distinct from another. These terms must not be regarded as superfluous; they are necessary to distinguish the divine Persons, as Scripture itself does.
In connection with the spiration of the Holy Ghost we must consider also the question of the Filioque, or whether the Holy Ghost was spirated also by the Son. The Eastern Church denied the Filioque, while the Western Church, on the basis of Scripture, affirmed it; for Holy Scripture ascribes the same relation of the Holy Ghost to the Son as it does to the Father. As He is called the Spirit of the Father, Matt. 10, 20, so He is also called the Spirit of the Son, Gal. 4, 6; and as He is sent of the Father, John 14, 26, so He is said to be sent also of the Son, John 15, 26. Because the Holy Spirit proceeds also from the Son, Christ could breathe and bestow Him upon His disciples, John 20, 22.
The actus persoooles are also called inward operations (opera ad intra) because they occur within the Godhead and extend from one Person to another (generation and spiration). From the inward operations we distinguish the outward operations (opera ad extra). or the works in which the three Persons of the Godhead cooperate, or concur (creation, redemption, sanctification, etc.). Of the inward operations the axiom holds: "The inward operations are divided." (Opera ad intra divisa sunt.) Of the outward operations the axiom obtains: "The outward operations are undivided."
(Opera ad extra sunt indivisa.) These axioms express the Scriptural truth that the inward operations are performed by individual Persons, while the outward operations are performed by the Three Persons in common, or together. If at times Scripture ascribes creation to the Father, redemption to the Son, and sanctification to the Holy Ghost, this is done by appropriation, which, however, does not exclude the divine operation of the other Persons. The only opus ad extra in which the Father and the Holy Ghost did not directly concur, was the work of redemption (the incarnation, suffering, death, resurrection, and exaltation of Christ); for while it is true that the Son was sent by the Father and sustained by Him in His redemptive work, and while it is equally true that He was anointed with the Holy Ghost (Ps. 45, 7; Heb. 1, 9; Acts 10, 38) for His work, Scripture ascribes the work of redemption to Christ alone, Eph. 2, 13; Col. 1, 20; 1 John 1, 7. To express this unique character of Christ's redemptive work, the dogmaticians have called it an opus mixtum, or a work which Christ accomplished alone, but in the performance of which He was not without the Father and the Holy Ghost. (For the actus personales compare Luther's exposition of the Three Symbols, St. L., X, 993 ff.)
The name Father is sometimes used essentially (οὐσιωδῶς), referring to the divine Persons equally (Jas. 1, 17 ; 2 Cor. 6, 17. 18 ; Luke 12, 32), and sometimes personally (ὑποστατικῶς). referring alone to the First Person of the Godhead, John 10, 30; 14, 9; 1 John 2, 23. So also the name Spirit is used essentially, John 4, 24, and personally, Matt. 12, 31; Mark 1, 10.
By the term περιχώρησις (immanentia, immeatio, circumincessio) is understood the mutual and most intimate inherence (inexistentia mutua et singularissima), by which one Person on account of the unity of the divine essence is within another, John 14, 11; 17, 21. By this term the Christian Church precludes the error of regarding the Three Persons as subsisting separately alongside one another. By the term equality Christian theology expresses the fact that one divine Person is in itself not greater than another, and by the term sameness, that the Three Persons have the same nature and consequently also cooperate in the same opera ad extra, John 5, 19. 17.
On the basis of Holy Scripture, Hollaz defines the Three Persons as follows: "a) God the Father is the First Person of the Godhead, neither begotten nor proceeding, but from eternity begetting the Son, the substantial image of Himself, and with the Son from eternity breathing forth the Holy Spirit, creating, preserving, and governing all things, sending His Son as the Redeemer and the Holy Ghost as the Sanctifier of the human race. b) The Son of God is the Second Person of the Godhead, begotten of the Father from eternity, of the same essence and majesty with the Father, who with the Father from eternity breathes forth the Holy Spirit and in the fulness of time assumed human nature in His own Person that He might redeem and save the human race. c) The Holy Spirit is the Third Person of the Godhead, of the same essence with the Father and the Son, who from eternity proceeds from the Father and the Son and in time is sent forth by both to sanctify the hearts of those who are to be saved." Doctr. Theol., p. 134
In connection with the terminology of the Church regarding the doctrine of God we may consider the debated question whether God may be logically defined or not. In replying to the question, our dogmaticians distinguish between "a perfect definition, which exactly conforms to accurate logical rules, and a general description, drawn from Scripture." (Gerhard.) The inadmissibility of a definition of God in the strict sense is argued, in the main, a) from the want of a genus, since God has no true and logical genus, and b) from the divine perfection of God, He being the Supreme Being, so that nothing is beyond Him. (Gerhard.) Nevertheless, though God cannot be logically defined as creatures are defined since He belongs in a class by Himself, a general description of God, drawn from Scripture, is sufficient for such a knowledge of God as is needed for salvation. Accordingly God has been described as "the first Being, who is of Himself and the Cause of all other things," or more completely, by Melanchthon (Loci Theol., I, 13): "God is a spiritual essence, intelligent, eternal, true, good, pure, just, merciful, most free, of vast power and wisdom- the eternal Father, who begat the Son, His own image, from eternity, and the Son, the coeternal image of the Father, and the Holy Spirit, proceeding from the Father and the Son."