There is only one God.
"I am the first, and I am the last, and besides Me there is no God" (Isaiah 44:6). There can be only one God, because only one can be supreme, all-powerful, and independent of all.
In God there are three Divine Persons - the Father, the Son, and the Holy Ghost.
In speaking of the "persons" in God, we do not use the term in exactly the same was we use it when speaking of people. We use it only for lack of a word to show our meaning better.
In speaking of a man as a "person," we mean that he is an intelligent being, acting individually for himself. The acts he performs belong to him and he is responsible for them-he himself, not his tongue, nor his mind, nor his whole body even, but the whole of himself.
We speak of three "Persons" in God because to each belongs something we cannot attribute to any other: His distinct origin.
From all eternity the Father begets the Son, and the Son proceeds from the Father. From all eternity the Father and Son breathe forth the Holy Ghost, and He proceeds from Them, as from one Source.
By the Blessed Trinity we mean one and the same God in three divine Persons.
The Father is God and the First Person of the Blessed Trinity. Omnipotence, and especially the work of creation, is attributed to God the Father.
God the Father could have created millions of beings instead of you yourself; but He chose you out of a love wholly underserved, saying, "I have loved thee with an everlasting love" (Jeremiah 31:3). Let us then cry in thanksgiving, "Abba, Father!" (Romans 8:15). Let us show our gratitude by avoiding all that could displease God the Father, by trying to please Him with virtue, by trying for greater perfection, in obedience to that injunction of Our Lord's: "You therefore are to be perfect, even as your Heavenly Father is perfect" (St. Matthew 5:48).
The Son is God and the Second Person of the Blessed Trinity. To God the Son we owe our redemption from sin and eternal death; by His death He gave us life.
For us God the Son debased Himself, taking the form of a servant,…"becoming obedient to death, even to death on a cross" (Philippians 2:8). In Holy Communion we are united with Him, for He Himself said: "He who eats My flesh, and drinks My blood, abides in Me and I in him" (St. John 6:57). In return we should be "other Christs," and, as the Apostle urged, "walk even as He walked."
The Holy Ghost is God and the Third Person of the Blessed Trinity. He manifests Himself in us particularly in our santification. The word "Ghost" applied to the Third Person means "Spirit."
At our Baptism God the Holy Ghost purifies us from all sin and fills our souls with divine grace, so that we become truly children of God, sons and heirs, and co-heirs with Jesus Christ. By Baptism we become living temples of the Holy Ghost: "Or do you not know that your members are the temple of the Holy Spirit, who is in you?" (1 Corinthians 6:19).
In return for such benefits we should make our body the instrument for the glory of God, keeping it from all stain of sin, adorning it with virtues. "Glorify God and bear Him in your body" (1 Corinthians 6:20). Let us keep our souls a sanctuary for the Holy Spirit, that God may be happy to dwell in us.
The three Divine Persons are really distinct from one another.
"So there is one Father, not three Fathers; one Son, not three Sons; one Holy Ghost, not three Holy Ghosts. And in this Trinity nothing is afore or after, nothing is greater or less; but the whole three Persons are co-eternal together, and copequal. So that in all things, as is aforesaid, the unity in Trinity, and the Trinity in unity is to be worshipped." (From the Athanasian Creed).
This is the simplest way by which the distinct origin of each Divine Person has been explained: God is a spirit, and the first act of a Spirit is to know and understand. God, knowing Himself from all eternity, brings forth the knowledge of Himself, His own image. This was not a mere thought, as our knowledge of ourselves would be, but a Living Person, of the same substance and one with the Father. This is God the Son. Thus the Father "begets" the Son, the Divine Word, the Wisdom of the Father.
"In the beginning was the Word, and the Word was with God; and the Word was God" (St. John 1:1).
God the Father, seeing His own Image in the Son, loves the Son; and God the Son loves the Father from all eternity. Each loves the other, because each sees in the other the Infinity of the Godhead, the beauty of Divinity, the Supreme Truth of God. The two Persons loving each other do not just have a thought, as human beings would have, but from Their mutual love is breathed forth, as it were, a Living Person, one with Them, and of Their own substance. This is God the Holy Ghost. Thus the Holy Ghost, the Spirit of Love, "proceeds" from the Father and the Son.
"But when the Advocate has come, whom I will send you from the Father, the Spirit of truth Who proceeds from the Father, He will bear witness concerning Me" (St. John 15:26).
But we are not to suppose that once God the Father begot the Son and now no longer does so, nor that once the love of the Father and the Son for each other breathed forth the Holy Ghost, but now no longer does. These truths are eternal, everlasting.
God the Father eternally knows Himself, and continues to know Himself, and thus continues to bring forth the Son. God the Father and God the Son continues to love each other, and their delight in each other continues to bring forth the Spirit of Love, God the Holy Ghost. In a similar way, fire has light and color. As long as there is fire, it continues to produce light. As long as there is fire with light, there is produced color. But all three exist at one and the same time.
In this imperfect way we vaguely see that God must necessarily be three Divine Persons, because only in that way can God with His Divine Knowledge and Will be complete in Himself.
Our Lord Jesus Christ spoke to us of the Blessed Trinity when before the Ascension He said to His Apostles: "Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost" (St. Matthew 28:19).
"And the Catholic Faith is this, that we worship one God in Trinity, and Trinity in unity. Neither confounding the Persons, nor diving the Substance…But the Godhead of the Father, of the Son, and of the Holy Ghost is one, the glory equal, themajesty co-eternal…The Father is made of none, neither created, nor begotten. The Son is the Father alone: not made, nor created, but begotten. The Holy Ghost is the Father and the Son: not made, nor created, nor begotten, but proceeding…And in this Trinity nothing is afore or after, nothing is greater or less, but the whole three Persons are co-eternal together, and co-equal" (From the Athanasian Creed).
The three divine Persons are perfectly equal to one another, because all are one and the same God.
"Such as the Father is, such is the Son, and such is the Holy Ghost. The Father Uncreated, the Son Uncreated, and the Holy Ghost Uncreated. The Father Infinite, the Son Infinite, and the Holy Ghost Infinite. The Father Eternal, the Son Eternal, and the Holy Ghost Eternal, and yet they are not Three Eternals but One Eternal. As also there are not Three Uncreated, nor Three Infinite, but One Uncreated, and One Infinite. So likewise the Father is Almighty, the Son Almighty, and the Holy Ghost Almighty. And yet they are not Three Almighties, but One Almighty." (From the Athanasian Creed).
All three Persons are equal in every way, equal in power and glory. The attributes and external works of God are common to all three Persons. However, in human speech we attribute certain works to each Person.
Thus we attribute to the Father the works of creation, to the Son the work of redemption, and to the Holy Ghost the work of sanctification. In reality these works belong equally to all three.
The three divine Persons, though really distinct from one another, are one and the same God because all have one and the same divine nature.
Each of the divine Persons is God.
"So the Father is God, the Son is God, and the Holy Ghost is God. And yet they are not three Gods, but one God. So likewise the Father is Lord, the Son is Lord, and the Holy Ghost is Lord. And yet they are not three Lords but one Lord. For, like as we are compelled by Christian truth to acknowledge every Person by Himself to be God and Lord, so are we forbidden by the Catholic Religion to say there be three Gods or three Lords." (From the Athanasian Creed).
There are three Persons, but only one Being. The Father is neither the Son nor the Holy Ghost. The Son is neither the Father nor the Holy Ghost. The Holy Ghost is neither the Father nor the Son.
It was the Son Who became man and died for us, not the Father or the Holy Spirit. But when we receive God the Son in Holy Communion, we also spiritually receive God the Father and God the Holy Ghost. The Blessed Trinity then dwells in us as in a Temple.
We cannot fully understand how the three divine Persons, though really distinct from one another, are one and the same God, because this is a supernatural mystery.
A supernatural mystery is a truth which we cannot fully understand, but which we firmly believe because we have God's word for it. A supernatural mystery is above reason, but not contrary to it. No man can explain a mystery; neither can anyone know it unless it is revealed by God. "Great art thou, O Lord, in counsel, and incomprehensible in thought" (Jeremiah 32:19).
It is not unreasonable to believe in a supernatural mystery. There are many natural mysteries around us that no one has yet been able to explain, yet we believe them: electricity, magnetism, force, and many of the processes of life.
The doctrine of the Blessed Trinity is a strict mystery; that is, we cannot learn it from reason, nor understand it completely, even after it has been revealed to us.
The doctrine contains two truths our reason cannot fully understand: (1) that there is only one God; and (2) that each of the three Persons is God. We can understand each of these truths separately, but not when taken together.
The mystery of the Blessed Trinity is not a contradiction. We do not say that there are three gods in one God, nor that the three divine Persons are one Person.
We only say that there are three Persons in one God, that is, three Persons, and one nature or essence. Somewhat similarly, the soul of man has will, understanding, and memory, but it is only one soul. Also, the sun has form, light, and heat, but is only one sun. Three flames put together make only one flame.
We believe in the mystery of the Blessed Trinity because God Himself revealed it to us.
"Thy word is Truth" (St. John 17:17). The mystery of the Blessed Trinity is the greatest of all mysteries. We believe it because God has revealed it to us, but we cannot fully understand it. It would be foolish to refuse to believe just because we cannot understand; that would be like a blind man who refuses to believe there is a sun, because he cannot see it. Is God limited because we are:
The Jews did not explicitly believe in the Blessed Trinity, although there are re ferences to the mystery in the Old Testament.
Before making man, God said: "Let Us make man to Our own image" (Genesis 1:26). David says: "The Lord said to my Lord, Sit on my right hand."
Our Lord Jesus Christ revealed the mystery. He said:
"Go therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit" (St. Matthew 28:19).
"But when the Advocate has come, Whom I will send you from the Father, the Spirit of truth Who proceeds from the Father, He will bear witness concerning Me" (St. John 15:26).
The Blessed Trinity manifested Itself at the baptism of Jesus Christ.
God the Father spoke from the Heavens; God the Son was baptized; God the Holy Ghost descended in visible form, in the form of a dove.
We profess our faith in the Blessed Trinity especially when we make the sign of the cross.
We also honor the Blessed Trinity every time we say the doxology or "prayer of praise": "Glory be to the Father, and to the Son, and to the Holy Ghost. As it was in the beginning, is now, and ever shall be world without end."
The Feast of the Blessed Trinity, called Trinity Sunday, is kept on the first Sunday after Pentecost.
All the sacraments are administered in the name of the Blessed Trinity.
On our death-bed the Church through the priest will comfort us with the words: "Even though he hath sinned, he hath not denied the Father, the Son, and the Holy Ghost."