First, however, allow me to explain what is meant by the Blessed Trinity. The Blessed Trinity is one God in three persons. This mystery is the very foundation of our religion. Without knowledge of this truth we cannot begin to understand our redemption by the Son of God. Jesus Christ and the Holy Ghost taught the mystery to us, and apart from this teaching, found both in Scripture, specifically the New Testament, and the Tradition of the Church, it is utterly unknown. No other monotheistic religion teaches it. It can not be inferred or deduced by human reason alone. It is utterly unique, and utterly beyond human comprehension.
There are, however, hints of the Trinity in creation and in the Old Testament. St. Bonaventure delighted in finding the Trinity in everything around him. It is true. For example, there are three aspects of time: past, present and future. There are three kingdoms in creation: mineral, vegetable and animal. Likewise there are hints in our religion. There is the triple office of Our Blessed Lord: Prophet, Priest and King. There were three members of the Holy Family: Joseph, Mary and Jesus. There are three parts to each sacrament of the Church: intention, matter and form. Our Blessed Lord hung on the cross for three hours.
The mystery had to have been partly known to the Patriarchs as is evidenced by the Old Testament. In the time of the Old Testament the Jewish priests repeated the Name of God three times whenever they blessed the people. Isaias tells us that the seraphim in heaven, as we still do today at each and every Mass, cry, “Holy, holy, holy, Lord God of hosts” (Is. 6. 3). When God created from nothing the world, He said, “Let us make man” (Gen. 1. 26). Finally, King David says, “The Lord said to My Lord, sit on My right hand.”
However, until the Incarnation the mystery of the Blessed Trinity remained hidden, veiled in a cloud, which was only dispelled under the world altering dispensation of the New Law. Our Blessed Lord said, “The Father no man knoweth but the Son, and He to whom the Son shall reveal Him” (Matt. 11. 27). Our Blessed Lord revealed the mystery plainly to the Church when He said to His apostles before His ascension: “Go and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost” (Matt. 28. 19). We as a Church express our belief in what Our Blessed Lord revealed when we recite the Nicene Creed and the Apostles’ Creed, it is expressed in the words of Baptism, in the other sacraments, and in all consecrations and blessings.
At the risk of a gross oversimplification of this theological inquiry, we may proceed thus: God is perfect. God has a perfect idea of Himself. This idea, because it is a perfectly divine idea of the perfectly divine Being, it is God, Himself. And so the Son of God, the Logos, proceeds from the Father. The Father loves the Son with a perfectly divine love, and the Son loves the Father with a perfectly divine love. This love, because it is the perfect love of a perfect Being for a perfect Being, is God, Himself. Thus, the Holy Ghost proceeds, or spirates, from the Father and the Son.
Objection: Why does it have to be so complicated? This is really hard to understand. A couple of people from the Jehovah Witnesses knocked on my door and gave me a far more plausible explanation, explaining that Jesus wasn’t really God, but Michael the Archangel. Isn’t that easier to understand?
Answer: At no time did Our Blessed Lord say that the Truth would be easy to understand or uncomplicated. He promised that the Holy Ghost would come and teach us all things (Jn 14:26), not that we would comprehend completely and all at once everything that has been revealed. The Christian religion is not for children, but for grown ups, as St. Paul explained to the Corinthians (1 Cor. 13:11). While we are to trust in God like children (Matt 18:3-5), that does not mean we must be immature in our religion or must accept immature explanations of the faith, especially those immature explanations of the faith that are contrary to what the Church has always taught. Throughout history there has been no shortage of immature "simple" explanations, from Gnostic dualism to Protestantism's sola fide and sola scriptura. They all seem plausible until held up against the light of what the Scriptures actually say, at which point they are exposed as nothing more than human systems of thought that are used to judge and ultimately limit, sinfully it should be stated, the Word of God.
One such immature explanation of the Trinity and the nature of Our Blessed Lord is the one put forth by groups like the Jehovah Witnesses, who are doing nothing more than re-wrapping the old Arian heresy from the third and fourth centuries (which, by the way, makes up a fundamental aspect of Islam). They don’t so much as deny the Trinity as they deny the Divinity of Christ. Their approach doesn’t remain so simple and straight forward once one presents them with certain passages from Scripture that contradict their simple explanation, such as the very first words of St. John’s Gospel, which says “In the beginning was the Word, and the Word was with God, and the Word was God… And the Word was made flesh, and dwelt among us” (Jn 1:1,14). Or how about when St. Thomas address Jesus as, “My Lord, and my God” (Jn 20:28)? Or how about when Jesus unambiguously proclaims: “I and the Father are one” (Jn 10:30)? St. Paul wasn’t coy about the subject when he wrote plainly enough, “for in him dwelleth all the fullness of the Godhead corporeally” (Col 2:9). The interpretive gymnastics that our Jehovah Witnesses must perform to explain away these passages from the Bible makes Catholic dogma and theology seem as simple as a Dr. Seuss picture book.
If you are a Catholic (and everybody ought to be):
*You must profess that there is one God, and only one God, and that this one God is God in Three Persons, the Father, the Son, and the Holy Ghost. This is a great mystery of our faith, but just because it is a mystery doesn’t mean it is not true, or true for just some people, but not others. This means that God, the God of all and everybody, even Jews and Muslims, is objectively a Trinity of Persons, and that those others are either mistaken about the God they worship or are not worshipping God at all.
*You must believe that the Trinity was taught to us by Christ, Himself, as is clear from the Bible.
*You must profess that Jesus Christ is the Son of God, the Second Person of the Blessed Trinity, made man, hence He is God, Himself.
*You must profess that the Second Divine Person of the Blessed Trinity became man in the womb of the Blessed Virgin Mary by the action of the Holy Ghost a the moment of the Annunciation.
*You must profess that Jesus Christ is true God and true man, that there are two natures, human and divine, which, despite their intimate union, are distinct in the one divine person of Christ.
*You must profess that the Holy Ghost is the Third Person of the Blessed Trinity, and is, therefore, God, Himself.
*You must profess that the Holy Ghost dispenses the graces which Christ merited by the sacrifice of the Cross, and, therefore, the assistance of the Holy Ghost is absolutely necessary for salvation.
*You must believe (even if you don’t express it verbally in the liturgy) that the Holy Ghost proceeds from the Father AND the Son.
*You ought to begin every prayer and every endeavor by invoking the Holy Trinity by making the Sign of the Cross while saying: “In the Name of the Father, and the Son, and the Holy Ghost (or Spirit).”
*You ought to pray daily for a deeper understanding of the Trinity. The revelation of the Trinity is a revelation about the interior life of God, which demonstrates the intimacy of the relationship between the elect and God through Jesus Christ. The revelation of the Trinity is a great gift!
I believe in one God, the Father almighty, maker of heaven and earth, and of all things visible and invisible. And in one Lord, Jesus Christ, the only-begotten Son of God. Born of the Father before all ages. God of God, Light of Light, true God of true God. Begotten, not made, of one substance with the Father. By Whom all things were made. Who for us men and for our salvation came down from heaven. And He became flesh by the Holy Ghost of the Virgin Mary; and was made man. He was also crucified for us, suffered under Pontius Pilate, and was buried. And on the third day He rose again according to the Scriptures. He ascended into heaven and sits at the right hand of the Father. He will come again in glory to judge the living and the dead. And of His kingdom there will be no end. And i believe in the Holy Ghost, the Lord and Giver of life, Who proceeds from the Father and the Son. Who together with the Father and the Son is adored and glorified; and Who spoke through the Prophets. And one, holy, Catholic, and Apostolic Church. I confess one baptism for the forgiveness of sins. And I await the resurrection of the dead. And the life of the world to come. Amen.
It is truly meet and just, right and for our salvation, that we should at all times, and in all places, give thanks unto Thee, O holy Lord, Father almighty, eternal God; Who, together with Thine only-begotten Son, and the Holy Ghost, art one God, one Lord: not in the oneness of a single Person, but in the Trinity of one substance. For what we believe by Thy revelation of Thy glory, the same do we believe of Thy Son, the same of the Holy Ghost, without difference or separation. So that in confessing the true and everlasting Godhead, distinction in persons, unity in essence, and equality in majesty may be adored. Which the Angels and Archangels, the Cherubim also and Seraphim do praise: who cease not daily to cry out, with one voice saying: Sanctus, Sanctus, Sanctus...
Whosoever will be saved, before all things it is necessary that he hold the Catholic Faith. Which Faith except everyone do keep whole and undefiled, without doubt he shall perish everlastingly. And the Catholic Faith is this, that we worship one God in Trinity and Trinity in Unity. Neither confounding the Persons, nor dividing the Substance. For there is one Person of the Father, another of the Son, and another of the Holy Ghost. But the Godhead of the Father, of the Son and of the Holy Ghost is all One, the Glory Equal, the Majesty Co-Eternal. 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 Incomprehensible, the Son Incomprehensible, and the Holy Ghost Incomprehensible. The Father Eternal, the Son Eternal, and the Holy Ghost Etneral and yet they are not Three Eternals but One Eternal. As also there are not Three Uncreated, nor Three Incomprehensibles, but One Uncreated, and One Uncomprehensible. So likewise the Father is Almighty, the Son Almighty, and the Holy Ghost Almighty. And yet they are not Three Almighties but One Almighty.
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 Lord, and the Holy Ghost Lord. And yet not Three Lords but One Lord. For, like as we are compelled by the Christian verity 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. The Father is made of none, neither created, nor begotten. The Son is of the Father alone; not made, nor created, but begotten. The Holy Ghost is of the Father, and of the Son neither made, nor created, nor begotten, but proceeding.
So there is One Father, not Three Fathers; one Son, not Three Sons; One Holy Ghost, not Three Holy Ghosts. And in this Trinity none is afore or after Other, None is greater or less than Another, but the whole Three Persons are Co-eternal together, and Co-equal. So that in all things, as is aforesaid, the Unity is Trinity, and the Trinity is Unity is to be worshipped. He therefore that will be saved, must thus think of the Trinity.
Furthermore, it is necessary to everlasting Salvation, that he also believe rightly the Incarnation of our Lord Jesus Christ. For the right Faith is, that we believe and confess, that our Lord Jesus Christ, the Son of God, is God and Man.
God, of the substance of the Father, begotten before the worlds; and Man, of the substance of His mother, born into the world. Perfect God and Perfect Man, of a reasonable Soul and human Flesh subsisting. Equal to the Father as touching His Godhead, and inferior to the Father as touching His Manhood. Who, although He be God and Man, yet He is not two, but One Christ. One, not by conversion of the Godhead into Flesh, but by taking of the Manhood into God. One altogether, not by confusion of substance, but by Unity of Person. For as the reasonable soul and flesh is one Man, so God and Man is one Christ. Who suffered for our salvation, descended into Hell, rose again the third day from the dead. He ascended into Heaven, He sitteth on the right hand of the Father, God Almighty, from whence he shall come to judge the quick and the dead. At whose coming all men shall rise again with their bodies, and shall give account for their own works. And they that have done good shall go into life everlasting, and they that have done evil into everlasting fire. This is the Catholic Faith, which except a man believe faithfully and firmly, he cannot be saved.