How can we prove the existence of the Trinity from the scriptures?

Even though the term “Trinity” is never mentioned in the Scriptures, the mystery of the Most Holy Trinity is the central mystery of Christian faith and life (CCC 234). The doctrine declares that God exists as a unity of three distinct persons: Father, Son, and Holy Spirit.  Each of the persons is distinct from the other, yet identical in essence. At first glance, this might seem like one which is difficult to comprehend and indeed it is. No wonder it is called a “mystery”, something which is a divinely revealed truth whose very possibility cannot be rationally conceived before it is revealed and after revelation, whose inner essence cannot be fully understood by the finite created mind. The good news is that the doctrine of trinity is something that has been “divinely revealed” and hence can be found in the written Word of God. 

The first step would be to establish how many gods exist. The answer can be found in the following verses:

1. “Before me no god was formed, nor shall there be any after me.” – Isaiah 43:10
2. “I am the first and I am the last; besides me there is no god.” – Isaiah 44:6
3. “I am the Lord, and there is no other; besides me there is no god.” – Isaiah 45:5
4. “And this is eternal life, that they may know you, the only true God, and Jesus Christ whom you have sent.” – John 17:3

Having affirmed that, let’s move onto the next step of proving the doctrine of trinity – finding out whether the Bible talks anything about the divinity of Christ. My personal favourite for this is to look at what John has written down in his gospel, as its explicit emphasis is on the proclamation of the divinity of Jesus, that both God the Father and Jesus had the same essence (John 20:31). Maybe this is why, from the very beginning, the Apostle uses plain and simple language to present Jesus as God. He writes, “In the beginning was the Word, and the Word was with God, and the Word was God… And the Word became flesh and lived among us… From his fullness we have all received grace upon grace. The law indeed was given through Moses; grace and truth came through Jesus Christ…” (John 1:1-17). Here, by saying “the Word was with God”, John presents the Word as someone who is distinct from God the Father. At the same time, he proclaims the unity between both the Word and God the Father when he pens the following words, “the Word was God”. Then he goes on to reveal Jesus as the one whom he was referring to as “the Word” (John 1:14-17). This is not the only instance that Jesus is being presented as God in the Bible. For more information, kindly go through this article, which goes much deeper into this topic. 

Now that we have covered two-third of the journey to prove the existence of the Trinity from the Scriptures, let’s move on to the last leg, where we will be looking for scriptural proof, which substantiates the claim that the Holy Spirit is indeed God. A starting point for this could easily be the conversation between Peter and Ananias, Acts 5:3-4, where the first bishop of Rome uses the term “God” and “the Holy Spirit” interchangeably pointing out that those two words represent the same entity. In verse three, Peter accuses Ananias of lying to the Holy Spirit and in the very next verse says that he (Ananias) “did not lie to men but to God!” 

St. Paul, while talking about the true wisdom of God, says – “For the Spirit searches everything, even the depths of God. For what person knows a man’s thoughts except the spirit of the man which is in him? So also, no one comprehends the thoughts of God except the Spirit of God.” (1 Corinthians 2:10-11). Here, the Holy Spirit is presented as someone who is all knowing, a trait which is reserved only for God himself, and also as someone who is capable of comprehending “the thoughts of God”, which are infinite. No created being is capable of doing that (Romans 11:34). If the Holy Spirit is revealed to be able to do so, it necessarily means that the Spirit possesses infinite power, as only a being with infinite power is capable of grasping the thoughts of God, which would, in turn, necessarily mean that he is, in fact, God. 

Paul again presents the Holy Spirit as God in 1 Corinthians 6:19 when he calls the physical body that we have “a temple of the Holy Spirit”. Keep in mind that, in the first century, the church at Corinth was made up of both Jews and Gentile converts. To both these groups, the word “temple” can only refer to a place dedicated to the service or worship of God. Therefore, the Holy Spirit is again revealed to be God and our bodies as his temple. 

Let’s, for the final time, look at what Paul had to say about the Holy Spirit. This time he was addressing a Christian community whose faith was faltering because of strong Jewish influences. 

Therefore, as the Holy Spirit says, “Today, when you hear his voice, do not harden your hearts as in the rebellion, on the day of testing in the wilderness, where your fathers put me to the test and saw my works for forty years. Therefore, I was provoked with that generation, and said, ‘They always go astray in their hearts; they have not known my ways.’ As I swore in my wrath, ‘They shall never enter my rest.’” – Hebrews 3:7-11

The questions to be answered are: 

1. Whom did the “fathers” put to test in the wilderness? 
2. Whose works did Israelites witness for forty years?
3. Who got provoked by the actions of the Israelites and swore ‘They shall never enter my rest.’?

For all these questions, there is only one answer – Yahweh (you do the math).

Therefore, like any other Christian doctrine, the doctrine of the Trinity can be deduced from looking at revealed Scripture as a whole and not just a single verse. It is the doctrine that God, who is one and unique in his infinite substance or nature, is three really distinct persons: the Father, Son, and Holy Spirit. The three divine persons are co-equal, co-eternal, and consubstantial and deserve co-equal glory and adoration. A simple analogy that can shed some light into this is that of time. We have the past, the present and the future, but there is only one time. Each one of them is distinct from each other, but not separated, just like Trinity.