The Trinity? Who can understand that?

Someone who will to do the research to find someone who does understand it and learn.

What is the doctrine of the Trinity? The doctrine of the Trinity states that there is one God who eternally exists as three distinct Persons--the Father, Son, and Holy Spirit--and these three Persons are the one God. Another way to explain it is that God is one in essence and three in person. These definitions bring out the three fundamental truths which summarize the biblical teaching on the Trinity: (1) God is three Persons, (2) each Person is fully God, (3) there is only one God.[1]

God is one in essence, but three in Persons.

God has one nature, but three centres of consciousness.

That is, there is only one What in God, but there are three Whos.

There is one It, but three I's.

This is a mystery but not a contradiction.

It would be contradictory to say God was only one person, but also was three persons. Or that God is only one nature, but that he also had three natures. But to declare, as orthodox Christians do, that God is one in essence, eternally revealed in three distinct persons is not a contradiction.[When Critics Ask Norman Geisler]

The Trinity is a paradox rather than a contradiction. We have other paradoxes in nature like the wave particle duality of an electron or of light.

For further articles on this see Understanding the Trinity , Our Triune God, Critical Evidence for the Deity of Christ By Matt Perman

The doctrine of the trinity was first formulated by Tertullian, one of the early church fathers. The word trinity means 'threefold' or 'three in one'. The word trinity is not used in scripture but the doctrine is implicit in scripture. At its most simplest it is that God is one but in three persons God the Father, Son and Holy Spirit. The trinity is a mystery in that it cannot be comprehended by man yet it is still true, rather like the doctrines of predestination and free will. The scriptures reveal that God is one and that God is three, over emphasis on either one leads to error. Unitarianism accepts the existence of one God but ignores or denies his threeness (Jehovah's witnesses), tritheism accepts the threeness of God but rejects his unity.

One statement of faith declares the trinity as 'the eternal Godhead has revealed Himself as one God existing in three Persons, even the Father, the Son and the Holy Spirit; distinguishable, but indivisible in essence, co-eternal, co-equal and co-existent in attributes, power, nature and glory.'

The trinity in scripture:

The Old Testament emphasises that God is one, the new testament shows the three persons of the trinity.

Deu 6:4 (NIV) Hear, O Israel: The LORD our God, the LORD is one.

The Old Testament also indicates the trinity, in Gen 1:1 the word for God is the plural Elohim. In Gen 1:1-2 God created the heavens and the earth and the Spirit of God was hovering over the water. Gen 1:26 God says 'Let us make man in our image, in our likeness'.

Isa 61:1 (NIV) The Spirit of the Sovereign LORD is on me, because the LORD has anointed me to preach good news to the poor. He has sent me to bind up the brokenhearted, to proclaim freedom for the captives and release from darkness for the prisoners,

The trinity is most clearly seen in John’s gospel in the relationship between the Son, Father and Holy Spirit.

John 14:26 (NIV) But the Counsellor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.

John 15:26 (NIV) "When the Counsellor comes, whom I will send to you from the Father, the Spirit of truth who goes out from the Father, he will testify about me.

John 16:12-15 (NIV) "I have much more to say to you, more than you can now bear. 13 But when he, the Spirit of truth, comes, he will guide you into all truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. 14 He will bring glory to me by taking from what is mine and making it known to you. 15 All that belongs to the Father is mine. That is why I said the Spirit will take from what is mine and make it known to you.

The baptism of Jesus reveals the Father and the Spirit as does the command to baptise disciples in the great commission.

Mat 3:16-17 (NIV) As soon as Jesus was baptised, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and lighting on him. 17 And a voice from heaven said, "This is my Son, whom I love; with him I am well pleased."

Mat 28:19 (NIV) Therefore go and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit,

Other references to the trinity in the epistles:

1 Cor 12:4-6 (NIV) There are different kinds of gifts, but the same Spirit. 5 There are different kinds of service, but the same Lord. 6 There are different kinds of working, but the same God works all of them in all men.

2 Cor 13:14 (NIV) May the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all.

Gal 4:6 (NIV) Because you are sons, God sent the Spirit of his Son into our hearts, the Spirit who calls out, "Abba, Father."

Eph 4:4-6 (NIV) There is one body and one Spirit-- just as you were called to one hope when you were called-- 5 one Lord, one faith, one baptism; 6 one God and Father of all, who is over all and through all and in all.

1 Tim 2:5 (NIV) For there is one God and one mediator between God and men, the man Christ Jesus,

1 Pet 1:2 (NIV) who have been chosen according to the foreknowledge of God the Father, through the sanctifying work of the Spirit, for obedience to Jesus Christ and sprinkling by his blood: Grace and peace be yours in abundance.

Here is a useful proof of the Deity of Christ (the same designations are also used of God). In Rev 22:13 it is Christ talking.

(Rev 22:13 NIV) I am the Alpha and the Omega, the First and the Last, the Beginning and the End.