Why There is Only One God: One Supreme Cause

Scripture is explicit in equating the one God with the person of the Father:

“There is one body and one Spirit, just as also you were called in one hope of your calling; 5 one Lord, one faith, one baptism, 6 one God and Father of all who is over all and through all and in all.” Ephesians 4:4-5 NAS

“This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.” John 17:3 NAS

“yet for us there is but one God, the Father, from whom are all things and we exist for Him; and one Lord, Jesus Christ, by whom are all things, and we exist through Him.” 1 Corinthians 8:6 NAS

We have examined the identity of the one God as the person of the Father in some depth here. We can also see that this was the clear teaching of the orthodox church fathers of the ante-nicene and nicene eras, as can be seen here.

In this article we continue our series on ‘Why There is Only One God’. The question of how there is only one God comes to mind in light of the fact that while the Father is the one God, the Son and Spirit are also of the same divine nature as the Father. There are then three persons who are God, that is, Who possess the same divine nature; yet there are not three Gods, but only one, the person of the Father.

In light of this, why do the Son and Holy Spirit not constitute second and third Gods in addition to the Father, Who alone is the one God? The answer to this question is multifaceted. The person of the Father alone is the one God because He alone is the ‘uncaused Cause’ and ‘Head without a head’. Additionally, we may point to the unity of the Son and Spirit with the Father in respect to both their divine nature and their relationship to Him as reasons why They cannot be said to constitute second and third Gods. In this article, we will examine the first part of the answer given, that the Father alone is the uncaused Cause.

Firstly, what is meant by ‘uncaused Cause’? When we say that the one God alone is the uncaused Cause, we refer to the fact that He alone is without cause, origin, or source, while He Himself is the Cause, Source, and Origin of all else that exists. The one God is not only the cause and source of all creation, but also of His own Son by eternal generation and of His Holy Spirit by eternal procession. Being an ‘uncaused Cause’ then is unique to the person of the Father.

Another way to put this is that the Father alone is the First Cause of all. But by ‘First Cause’ we do not mean that the Father is in any way chronologically anterior to His Son and Spirit, but rather that He is logically first in that He is the Supreme Cause of all, to Whom everything that exists may be traced as its Source, including the Son and Holy Spirit through Whom God created all creation.

In showing this doctrine from scripture, let us begin by showing that God is the source of His Son and Holy Spirit, and after this that He Himself is entirely uncaused.

We see the Father demonstrated to be the Cause of the Son in the following passages of scripture:

“For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life.” (John 3:16 NKJV)

“And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.” (John 1:14 KJV)

“No man hath seen God at any time, the only begotten Son, which is in the bosom of the Father, he hath declared him.” (John 1:18 KJV)

“Whosoever believes that Jesus is the Christ is born of God: and every one that loves Him that begat loves Him also that is begotten of Him.” (1 John 5:21)

“The Lord possessed me in the beginning of his way, before his works of old. 23 I was set up from everlasting, from the beginning, or ever the earth was. 24 When there were no depths, I was brought forth; when there were no fountains abounding with water. 25 Before the mountains were settled, before the hills was I brought forth:” (Proverbs 8:22-25 KJV)

“For as the Father hath life in himself; so hath he given to the Son to have life in himself;” (John 5:26 KJV)

Likewise scripture testifies the the Father is the source of His Holy Spirit:

“But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:” (John 15:26 KJV)

So we see scripture’s clear teaching that the persons of the Son and Spirit have the person of the Father as Their source; thus the Father is unique among the persons of the Trinity as being personally the First Cause of all. And having the Father as Their own Cause and Source, the Son and Holy Spirit of God have no other nature than that of the only true God Whose Son and Spirit They are, eternally having the paternal divinity from the Father, the Son by His eternal generation, and the Holy Spirit as He eternally proceeds from the Father.

While we have shown that the Son and Holy Spirit have Their Source as the Father, the scriptures also clearly teach that the Father is alone without cause or source of any kind:

“O the depth of the riches both of the wisdom and knowledge of God! how unsearchable are his judgments, and his ways past finding out! 34 For who hath known the mind of the Lord? or who hath been his counsellor? 35 Or who hath first given to him, and it shall be recompensed unto him again? 36 For of him, and through him, and to him, are all things: to whom be glory for ever. Amen.” (Romans 11:33-36 KJV)

“yet for us there is but one God, the Father, from whom are all things and we exist for Him; and one Lord, Jesus Christ, by whom are all things, and we exist through Him.” (1 Corinthians 8:6 NAS)

These verses demonstrate what is already clear. It is obvious and self-evident that God is uncaused and without source; for He Himself being the supreme cause of all cannot have a cause or source of His own. For as we have seen above, He is the Source of not only all creation, but also of His Son and Holy Spirit; He is then, the Source of all, as it says above “from Whom are all things”. For if the Father were originate and caused, He would be from something else; yet scripture declares that all things are from Him. He then, if He is the Cause of all, cannot Himself be caused, for if He Himself were caused and from another, then all things would not be caused by Him and be from Him, since He Himself would be caused by another. But all that is caused, and all that finds a source or origin can be traced back to the Father as its ultimate source, cause and origin; He then alone is the uncaused Cause of all, and unoriginate Origin of all.

This unique quality of the Father distinguishes Him from the other persons of the Trinity, and accounts for why scripture teaches that He in particular is “the only true God”, even though His Son and Spirit have the very same divine nature as He. It is not on the basis of His divinity that the Father in particular is the “one God”, for this divinity is shared by all three persons of the Trinity. Rather, it is because of the unique qualities the Father has of alone being the uncaused Cause of all, and of alone being the ‘Head without a head’, which we shall defer until the next post to discuss.

Now, we have seen proved from the scriptures that the person of the Father alone, Who is the only true God, is the uncaused Cause of all; not only of all creation, but we have also demonstrated from the scriptures that He is the Cause and Source of His only-begotten Son and Holy Spirit. We shall now conclude with testimonies witnessing to these truths from the ancient fathers of the church:

Eusebius of Caesarea

“Well then, rightly did the divine evangelist say that he was in the beginning, having attributed to him a source, that is to say, the begetting from the Father. For everything that is begotten from something has the one who has begotten him as source. And surely likewise he added, not “and the Word was in God,” but “and the Word was with God,” teaching that the one who was begotten, having also possessed the Father as source, is not somehow far from the Father, nor has been separated or moved to some great distance from him, but that he is present to him and exists together with him.” (On Ecclesiastical Theology, Book 2, Chapter 14)

“For the excellent and unique character of the ingenerate [that is, unbegotten or uncaused] and divine life of the Father, on account of which “he alone has immortality,” as was said by the holy Apostle, the Son alone could have, seeing as he was the image of the Father even in this respect. But he has the aforementioned life not like the Father, not without source nor ingenerate nor acquired by himself, but has received [this immortal life] from the Father. For thus he says, “For as the Father has life in himself, so also he has given the Son to have life in himself.” Therefore, the one has given, the other received.” (On Ecclesiastical Theology, Book 1, Chapter 20)

“But are you afraid, man, lest, having confessed that there are two hypostases, you introduce two sources and cast aside the monarchical divinity? Well then, learn that because there is one God who is without source and unbegotten, but the Son has been begotten from him, there will be one source and a single monarchy and kingship, since even the Son himself acknowledges his Father as source. “The head of Christ is God,” according to the Apostle. But are you anxious that one might have to accept that there are two gods if you confess that there are two hypostases of Father and Son? But know this too: that the man who grants that there are two hypostases of Father and Son is not compelled to say there are two Fathers, nor that there are two Sons, but will grant that one is the Father and the other is the Son. Thus, in the same way, it is not necessary for the man who posits two hypostases to grant that there are two gods. For we neither deem them equally worthy of honor, nor both without source and unbegotten, but deem the one [hypostasis] as unbegotten  and without source, while [we deem] the other as begotten and having the Father as his source. For this reason, even the Son himself teaches that his Father is also his God, when he says, “I go to my Father and to your Father and to my God and to your God.” Thus God is shown to be both Father and God of the Son himself.” (On Ecclesiastical Theology Book 2, Chapter 7)

Alexander of Alexandria

We have learnt that the Son is immutable and unchangeable, all-sufficient and perfect, like the Father, lacking only His “unbegotten.” He is the exact and precisely similar image of His Father. For it is clear that the image fully contains everything by which the greater likeness exists, as the Lord taught us when He said, ‘My Father is greater than I.’ And in accordance with this we believe that the Son always existed of the Father ; for he is the brightness of His glory, and the express image of His Father’s Person.’ But let no one be led by the word ‘always’ to imagine that the Son is unbegotten, as is thought by some who have their intellects blinded : for to say that He was, that He has always been, and, that before all ages, is not to say that He is unbegotten…

Therefore His own individual dignity must be reserved to the Father as the Unbegotten One, no one being called the cause of His existence : to the Son likewise must be given the honour which befits Him, there being to Him a generation from the Father which has no beginning ; we must render Him worship, as we have already said, only piously and religiously ascribing to Him the ‘was’ and the ‘ever,’ and the ‘before all ages ;’ not however rejecting His divinity, but ascribing to Him a perfect likeness in all things to His Father, while at the same time we ascribe to the Father alone His own proper glory of ‘the unbegotten,’ even as the Saviour Himself says, ‘My Father is greater than I.’ (Epistle of Alexander, Bishop of Alexandria, to Alexander, Bishop of Constantinople, from Theodoret’s, Ecclesiastical History, I.III – NPNF 3.39, 40.)

“Not that the Word is unbegotten, for the Father alone is unbegotten, but because the inexplicable subsistence of the only-begotten Son transcends the acute comprehension of the evangelists, and perhaps also of angels.” (Epistles on Arianism and the Deposition of Arius)

“Concerning whom we thus believe, even as the Apostolic Church believes. In one Father unbegotten, who has from no one the cause of His being, who is unchangeable and immutable, who is always the same, and admits of no increase or diminution; who gave to us the Law, the prophets, and the Gospels; who is Lord of the patriarchs and apostles, and all the saints. And in one Lord Jesus Christ, the only-begotten Son of God; not begotten of things which are not, but of Him who is the Father; not in a corporeal manner, by excision or division as Sabellius and Valentinus thought, but in a certain inexplicable and unspeakable manner, according to the words of the prophet cited above: Who shall declare His generation? Isaiah 53:8 Since that His subsistence no nature which is begotten can investigate, even as the Father can be investigated by none; because that the nature of rational beings cannot receive the knowledge of His divine generation by the Father. But men who are moved by the Spirit of truth, have no need to learn these things from me, for in our ears are sounding the words before uttered by Christ on this very thing, No man knows the Father, save the Son; and no man knows who the Son is, save the Father. Matthew 11:27 That He is equally with the Father unchangeable and immutable, wanting in nothing, and the perfect Son, and like to the Father, we have learned; in this alone is He inferior to the Father, that He is not unbegotten. For He is the very exact image of the Father, and in nothing differing from Him. For it is clear that He is the image fully containing all things by which the greatest similitude is declared, as the Lord Himself has taught us, when He says, My Father is greater than I.” (Epistles on Arianism and the Deposition of Arius)


“We believe in one Unbegotten God, Father Almighty, maker of all things both visible and invisible, that hath His being from Himself. And in one Only-begotten Word, Wisdom, Son, begotten of the Father without beginning and eternally; word not pronounced nor mental, nor an effluence of the Perfect, nor a dividing of the impassible Essence, nor an issue; but absolutely perfect Son, living and powerful (Heb. iv. 12), the true Image of the Father, equal in honour and glory. ” (Statement of Faith)

“For the Son is in the Father, as it is allowed us to know, because the whole Being of the Son is proper to the Father’s essence, as radiance from light, and stream from fountain; so that whoso sees the Son, sees what is proper to the Father, and knows that the Son’s Being, because from the Father, is therefore in the Father. For the Father is in the Son, since the Son is what is from the Father and proper to Him, as in the radiance the sun, and in the word the thought, and in the stream the fountain: for whoso thus contemplates the Son, contemplates what is proper to the Father’s Essence, and knows that the Father is in the Son. For whereas the Form and Godhead of the Father is the Being of the Son, it follows that the Son is in the Father and the Father in the Son.” (Discourse 3, Against the Arians)

“1. The Word is God from God; for ‘the Word was God,’ and again, ‘Of whom are the Fathers, and of whom Christ, who is God over all, blessed for ever. Amen.’ And since Christ is God from God, and God’s Word, Wisdom, Son, and Power, therefore but One God is declared in the divine Scriptures. For the Word, being Son of the One God, is referred to Him of whom also He is; so that Father and Son are two, yet the Monad of the Godhead is indivisible and inseparable. And thus too we preserve One Beginning of Godhead and not two Beginnings, whence there is strictly a Monarchy. And of this very Beginning the Word is by nature Son, not as if another beginning, subsisting by Himself, nor having
come into being externally to that Beginning, lest from that diversity a Dyarchy and Polyarchy should ensue; but of the one Beginning He is own Son, own Wisdom, own Word, existing from It. For, according to John, ‘in’ that ‘Beginning was the Word, and the Word was with God,’ for the Beginning was God; and since He is from It, therefore also ‘the Word was God.’ And as there is one Beginning and therefore one God, so one is that Essence and Subsistence which indeed and truly and really is, and which said ‘I am that I am,’ and not two, that there be not two Beginnings; and from the One, a Son in nature and truth, is Its own Word, Its Wisdom, Its Power, and inseparable from It. And as there is not another essence, lest there be two Beginnings, so the Word which is from that One Essence has no dissolution, nor is a sound significative, but is an essential Word and essential Wisdom, which is the true Son. For were He not essential, God will be speaking into the air, and having a body, in nothing differently from men; but since He is not man, neither is His Word according to the infirmity of man. For as the Beginning is one Essence, so Its Word is one, essential, and subsisting, and Its Wisdom. For as He is God from God, and Wisdom from the Wise, and Word from the Rational, and Son from Father, so is He from Subsistence Subsistent, and from Essence Essential and Substantive, and Being from Being.” (Discourse 4, Against the Arians)

Hilary of Poitiers

“He will be safe in asserting the one substance if he has first said that the Father is unbegotten, that the Son is born, that He draws His personal subsistence from the Father, that He is like the Father in might, honour and nature, that He is subject to the Father as to the Author of His being…” (De Synodis)

“And if any one hearing this text, For as the Father has life in Himself so also He has given to the Son to have life in Himself John 5:26; denies that the Son is like the Father even in essence, though He testifies that it is even as He has said; let him be anathema. For it is plain that since the life which is understood to exist in the Father signifies substance, and the life of the Only-begotten which was begotten of the Father is also understood to mean substance or essence, He there signifies a likeness of essence to essence.

16. With the Son’s origin as thus stated is connected the perfect birth of the undivided nature. For what in each is life, that in each is signified by essence. And in the life which is begotten of life, i.e. in the essence which is born of essence, seeing that it is not born unlike (and that because life is of life), He keeps in Himself a nature wholly similar to His original, because there is no diversity in the likeness of the essence that is born and that begets, that is, of the life which is possessed and which has been given. For though God begot Him of Himself, in likeness to His own nature, He in whom is the unbegotten likeness did not relinquish the property of His natural substance.” (De Synodis)

“For the same reason we have of one substance, not to teach that there is one solitary divine Person, but that the Son is born of the substance of God and subsists from no other source, nor in any diversity caused by a difference of substance. Surely again this is our faith, that He subsists from no other source, and He is not unlike the Father. Is not the meaning here of the word ὁμοούσιον that the Son is produced of the Father’s nature, the essence of the Son having no other origin, and that both, therefore, have one unvarying essence? As the Son’s essence has no other origin, we may rightly believe that both are of one essence, since the Son could be born with no substance but that derived from the Father’s nature which was its source.” (De Synodis)

“We deny that there are two incapable of birth, because God is one through the prerogative of being incapable of birth” (De Synodis)

“XXVI. If any man says that the Son is incapable of birth and without beginning, speaking as though there were two incapable of birth and unborn and without beginning, and makes two Gods: let him be anathema. For the Head, which is the beginning of all things, is the Son; but the Head or beginning of Christ is God: for so to One who is without beginning and is the beginning of all things, we refer the whole world through Christ.

60. To declare the Son to be incapable of birth is the height of impiety. God would no longer be One: for the nature of the one Unborn God demands that we should confess that God is one. Since therefore God is one, there cannot be two incapable of birth: because God is one (although both the Father is God and the Son of God is God) for the very reason that incapability of birth is the only quality that can belong to one Person only. The Son is God for the very reason that He derives His birth from that essence which cannot be born. Therefore our holy faith rejects the idea that the Son is incapable of birth in order to predicate one God incapable of birth and consequently one God, and in order to embrace the Only-begotten nature, begotten from the unborn essence, in the one name of the Unborn God. For the Head of all things is the Son: but the Head of the Son is God. And to one God through this stepping-stone and by this confession all things are referred, since the whole world takes its beginning from Him to whom God Himself is the beginning.” (De Synodis, Quoting and commenting on the decision of the Council of Sirmium against Photinius)

Cyril of Jerusalem

“Of One Only Father there is One Only-begotten Son: neither two Unbegotten , nor two Only-begotten; but One Father, Unbegotten (for He is Unbegotten who has no father); and One Son, eternally begotten of the Father; begotten not in time, but before all ages; not increased by advancement, but begotten that which He now is.” (Catechetical Lecture 11)

“We believe then In the Only-Begotten Son of God, Who Was Begotten of the Father Very God. For the True God begets not a false god, as we have said, nor did He deliberate and afterwards beget ; but He begot eternally, and much more swiftly than our words or thoughts: for we speaking in time, consume time; but in the case of the Divine Power, the generation is timeless. And as I have often said, He did not bring forth the Son from non-existence into being, nor take the non-existent into sonship : but the Father, being Eternal, eternally and ineffably begot One Only Son, who has no brother. Nor are there two first principles; but the Father is the head of the Son 1 Corinthians 11:3; the beginning is One.” (Catechetical Lecture 11)

Novation of Rome

“And He is reasonably affirmed to be in the form of God, in that He Himself, being above all things, and having the divine power over every creature, is also God after the example of the Father. Yet He obtained, this from His own Father, that He should be both God of all and should be Lord, and be begotten and made known from Himself as God in the form of God the Father. He then, although He was in the form of God, thought it not robbery that He should be equal with God. For although He remembered that He was God from God the Father, He never either compared or associated Himself with God the Father, mindful that He was from His Father, and that He possessed that very thing that He is, because the Father had given it Him.” (On the Trinity, Chapter 22)

“Because it is essential that He who knows no beginning must go before Him who has a beginning; even as He is the less as knowing that He is in Him, having an origin because He is born, and of like nature with the Father in some measure by His nativity, although He has a beginning in that He is born, inasmuch as He is born of that Father who alone has no beginning. He, then, when the Father willed it, proceeded from the Father, and He who was in the Father came forth from the Father; and He who was in the Father because He was of the Father, was subsequently with the Father, because He came forth from the Father — that is to say, that divine substance whose name is the Word, whereby all things were made, and without whom nothing was made. For all things are after Him, because they are by Him. And reasonably, He is before all things, but after the Father, since all things were made by Him, and He proceeded from Him of whose will all things were made. Assuredly God proceeding from God, causing a person second to the Father as being the Son, but not taking from the Father that characteristic that He is one God. For if He had not been born — compared with Him who was unborn, an equality being manifested in both — He would make two unborn beings, and thus would make two Gods. If He had not been begotten — compared with Him who was not begotten, and as being found equal — they not being begotten, would have reasonably given two Gods, and thus Christ would have been the cause of two Gods. Had He been formed without beginning as the Father, and He Himself the beginning of all things as is the Father, this would have made two beginnings, and consequently would have shown to us two Gods also…  But now, whatever He is, He is not of Himself, because He is not unborn; but He is of the Father, because He is begotten, whether as being the Word, whether as being the Power, or as being the Wisdom, or as being the Light, or as being the Son; and whatever of these He is, in that He is not from any other source, as we have already said before, than from the Father, owing His origin to His Father, He could not make a disagreement in the divinity by the number of two Gods, since He gathered His beginning by being born of Him who is one God. In which kind, being both as well only-begotten as first-begotten of Him who has no beginning, He is the only one, of all things both Source and Head. And therefore He declared that God is one, in that He proved Him to be from no source nor beginning, but rather the beginning and source of all things.” (On the Trinity, Chapter 31)

Justin Martyr

“And now I shall again recite the words which I have spoken in proof of this point. When Scripture says, ‘The Lord rained fire from the Lord out of heaven,’ the prophetic word indicates that there were two in number: One upon the earth, who, it says, descended to behold the cry of Sodom; Another in heaven, who also is Lord of the Lord on earth, as He is Father and God; the cause of His power and of His being Lord and God.” (Dialogue With Trypho, Chapter 129)

“I shall give you another testimony, my friends, from the Scriptures, that God begot before all creatures a Beginning, [who was] a certain rational power [proceeding] from Himself, who is called by the Holy Spirit, now the Glory of the Lord, now the Son, again Wisdom, again an Angel, then God, and then Lord and Logos; and on another occasion He calls Himself Captain, when He appeared in human form to Joshua the son of Nave (Nun). For He can be called by all those names, since He ministers to the Father’s will, and since He was begotten of the Father by an act of will; just as we see happening among ourselves: for when we give out some word, we beget the word; yet not by abscission, so as to lessen the word [which remains] in us, when we give it out: and just as we see also happening in the case of a fire, which is not lessened when it has kindled [another], but remains the same; and that which has been kindled by it likewise appears to exist by itself, not diminishing that from which it was kindled. The Word of Wisdom, who is Himself this God begotten of the Father of all things, and Word, and Wisdom, and Power, and the Glory of the Begetter, will bear evidence to me, when He speaks by Solomon the following…” (Dialogue With Trypho, Chapter 61)

“For if you had understood what has been written by the prophets, you would not have denied that He was God, Son of the only, unbegotten, unutterable God.” (Dialogue With Trypho, Chapter 126)

Quote from Eusebius taken from: Eusebius Pamphilius, On Ecclesiastical Theology, trans. Kelly McCarthy Sproerl and Markus Vinzent (Washington, D.C.: The Catholic University of America Press, 2017).

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