On the basis of Scripture itself, Christians throughout the centuries have professed belief in the Holy Trinity, the Son and the Holy Spirit, who are co-equal, co-existent and co-eternal. This is because the following three things are very clearly taught in Scripture:
(1) There is only one God, who is eternal and immutable (unchanging). (Deut. 6:4; Isa. 43:10; Mal. 3:6; Mark 12:29; John 17:3; 1 Tim. 2:5; Jam. 2:19)
(2) There are three eternal Persons – the Father, the Son, and the Holy Spirit. These Persons are never identified with one another – that is, they are carefully differentiated as distinct Persons. The Father is not the Son, nor the Son the Holy Spirit, and nor is the Holy Spirit the Father. (Matt: 3:13-17; 28:19; Luke 10:22; John 1:1, 2; 3:16, 17; 15:26; 16:7; 17:1-26; 2 Cor. 13:14)
(3) The Father, the Son, and the Spirit, are identified as being full Deity – that is, the Bible teaches the Deity of the Father, the Deity of Christ and the Deity of the Holy Spirit. (Isa. 9:6; John 17:3; John 1:1, 18; 8:58; 20:28; Phil. 2:5-11; Col. 2:9; Titus 2:13; Heb 1:8; 2 Pet. 1:1; Acts 5:3, 4; 2 Cor. 3:17, 18)
Here’s a short video I put together where Dennis (the Christian) is explaining to Greg (an Aussie Jehovah’s Witness) why he believes in the Trinity. Enjoy!