What is the Trinity?
The word "trinity" is a term used to denote the Christian doctrine 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. In other words, each is fully divine in nature, but each is not the totality of the other persons of the Trinity. Each has a will, loves, and says "I", and "You" when speaking. The Father is not the same person as the Son who is not the same person as the Holy Spirit who is not the same person as the Father. Each is divine, yet there are not three gods, but one God. There are three individual subsistences, or persons. The word "subsistence" means something that has a real existence. The word "person" denotes individuality and self awareness. The Trinity is three of these, though the latter term has become the dominant one used to describe the individual aspects of God known as the Father, the Son, and the Holy Spirit.
Included in the doctrine of the Trinity is a strict monotheism which is the teaching that there exists in all the universe a single being known as God who is self-existent and unchangeable (Isaiah 43:10; 44:6,8). Therefore, it is important to note that the doctrine of the trinity is not polytheistic as some of its critics proclaim. Trinitarianism is monotheistic by definition and those who claim it is polytheistic demonstrate a lack of understanding of what it really is.
The Trinity God is three persons
Each person is divine
There is only one God.
Many theologians admit that the term "person" is not a perfect word to describe the three individual aspects/foci found in God. When we normally use the word person, we understand it to mean physical individuals who exist as separate beings from other individuals. But in God there are not three entities, nor three beings. God, is a trinity of persons consisting of one substance and one essence. God is numerically one. Yet, within the single divine essence are three individual subsistences that we call persons.
Each of the three persons is completely divine in nature though each is not the totality of the Godhead.
Each of the three persons is not the other two persons.
Each of the three persons is related to the other two, but are distinct from them.
The word "trinity" is not found in the Bible. But this does not mean that the concept is not taught there. The word "bible" is not found in the Bible either, but we use it anyway. Likewise, the words "omniscience," which means "all knowing," "omnipotence," which means "all powerful," and "omnipresence," which means "present everywhere," are not found in the Bible either. But we use these words to describe the attributes of God. So, to say that the Trinity isn't true because the word isn't in the Bible is an invalid argument.
Is there subordination in the Trinity?
There is, apparently, a subordination within the Trinity in regard to order but not substance or essence. We can see that the Father is first, the Son is second, and the Holy Spirit is third. The Father is not begotten, but the Son is (John 3:16). The Holy Spirit proceeds from the Father (John 5:26). The Father sent the Son (1 John 4:10). The Son and the Father send the Holy Spirit (John 14:26; 15:26). The Father creates (Isaiah 44:24), the Son redeems (Gal. 3:13), and the Holy Spirit sanctifies (Rom. 15:16).
This subordination of order does not mean that each of the members of the Godhead are not equal or divine. For example, we see that the Father sent the Son. But this does not mean that the Son is not equal to the Father in essence and divine nature. The Son is equal to the Father in his divinity, but inferior in his humanity. A wife is to be subject to her husband but this does not negate her humanity, essence, or equality. By further analogy, a king and his servant both share human nature. Yet, the king sends the servant to do his will. Jesus said, "For I have come down from heaven, not to do My own will, but the will of Him who sent Me" (John 6:38). Of course Jesus already is King, but the analogy shows that because someone is sent, it doesn't mean they are different than the one who sent him.
Critics of the Trinity will see this subordination as proof that the Trinity is false. They reason that if Jesus were truly God, then He would be completely equal to God the Father in all areas and would not, therefore, be subordinate to the Father in any way. But this objection is not logical. If we look at the analogy of the king and in the servant we certainly would not say that the servant was not human because he was sent. Being sent does not negate sameness in essence. Therefore, the fact that the Son is sent does not mean that He is not divine any more than when my wife sends me to get bread, I am not human. Is this confusing?
Another important point about the Trinity is that it can be a difficult concept to grasp. But this does not necessitate an argument against its validity. On the contrary, the fact that it is difficult is an argument for its truth. The Bible is the self revelation of an infinite God. Therefore, we are bound to encounter concepts which are difficult to understand -- especially when dealing with an incomprehensible God who exists in all places at all times. So, when we view descriptions and attributes of God manifested in the Father, the Son, and the Holy Spirit, we discover that a completely comprehensible and understandable explanation of God's essence and nature is not possible. What we have, however, done is derive from the Scripture the truths that we can grasp and combine them into the doctrine we call The Trinity. The Trinity is, to a large extent, a mystery. After all, we are dealing with God Himself.
It is the way of the cults to reduce biblical truth to make God comprehensible and understandable by their minds. To this end, they subject God's word to their own reasoning and end in error. The following verses are often used to demonstrate that in the doctrine of the Trinity is indeed biblical. Matt. 28:18, Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit, 1 Cor. 12:4-6, Now there are varieties of gifts, but the same Spirit. 5And there are varieties of ministries, and the same Lord. 6And there are varieties of effects, but the same God who works all things in all persons. 2 Cor. 13:14, The grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit, be with you all. Eph. 4:4-7, There is one body and one Spirit, just as also you were called in one hope of your calling; 5one Lord, one faith, one baptism, 6one God and Father of all who is over all and through all and in all. 7But to each one of us grace was given according to the measure of Christ's gift. 1 Pet. 1:2, "according to the foreknowledge of God the Father, by the sanctifying work of the Spirit, that you may obey Jesus Christ and be sprinkled with His blood: May grace and peace be yours in fullest measure." Jude 20-21, "But you, beloved, building yourselves up on your most holy faith; praying in the Holy Spirit; 21keep yourselves in the love of God, waiting anxiously for the mercy of our Lord Jesus Christ to eternal life."