A concept invented around the fourth century CE and solidified in The Nicene Creed, by a council presided over by the Emperor
Constantine. Despite being one of the tenets of modern Christianity, there is no actual mention of
a Trinity in the Bible, the closest reference perhaps being Matthew 28:19. A similar reference in I John (5:7) is confined to the footnotes of many Bible translations, since it's authenticity is subject to much suspicion. Translations of this verse include:
NIV: there are three that testify: the Spirit, the water and the blood; and the three are in agreement.
KJV: For there are three that bear record in heaven, the Father, the Word, and the
Holy Ghost: and these three are one.
NLV: So we have these three witnesses -- the Spirit, the water, and the blood--and all three agree.
However, there is no reference to the "Word", or "Holy Ghost" in the sense of a trinity-like association in any Greek
manuscript before the sixteenth century, thus it is rejected by most scholars.
In contrast, there are passages from the Bible that actually contradict the idea of
a trinity, namely:
Dueteronomy 6:4 (KJV): Hear, O Israel: The LORD our God is one LORD
Repeated yet again:
Mark 12:29 (KJV): And Jesus answered him, The first of all
the commandments is, Hear, O Israel; The Lord our God is one Lord
There are too references to Jesus and God as two separate entities (bearing in mind that "God" itself is supposedly the Father, Son and Holy Spirit as One):
Mark 16:19 (KJV): So then after the Lord had spoken unto them, he was received up into heaven, and sat on the right
hand of God.
Such inconsistencies have led some religious offshoots (Most notably the Jehovah's Witnesses) to reject the notion of
the trinity. Such questioning of the existence of
the Trinity causes hot debate amongst scholars and theologians, and conservative Christians. However, there is indisputable evidence that suggests the Trinity is nothing more than a man-made concept, tacked onto the end of an existing doctrine.