The doctrine of trinity is scriptural.
There is one Supreme Being, God, who eternally exists in three Persons - the Father, the Son, and the Holy Spirit.Isaiah 45:5 I am the LORD, and there is none else, there is no God beside me: I girded thee, though thou hast not known me:
These indicate plurality within the Godhead:Genesis 1:26 And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.
Genesis 11:7 Go to, let us go down, and there confound their language, that they may not understand one another's speech.
Jesus is fully God and fully man, and possesses all divine attributes.
Colossians 2:8-9
8 Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ.
9 For in him dwelleth all the fulness of the Godhead bodily.
Jesus is neither the Father nor the Holy Spirit. Here we see the activity of all three Persons in the Godhead:
- Jesus baptised,
- God the Father testified of Jesus' eternal sonship,
- and the Holy Spirit descended upon JesusMatthew 3:16-17
16 And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him:
17 And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.