John 1
1 In the beginning was the Word, and the Word was with God, and the Word was God.
2 The same was in the beginning with God.
3 All things were made by him; and without him was not any thing made that was made.
4 In him was life; and the life was the light of men.
5 And the light shineth in darkness; and the darkness comprehended it not.
Jesus Christ is the Word. These verses reveal that the Trinity always existed. "The Word was with God," shows us a relationship. "The Word was God" speaks about the same God that says in Genesis "In the beginning."
Jesus is the truth and life, the light. Without Him, mankind lives a lie and is dead, the darkness.
The Gospel of John will leave the reader without doubt that Christ is Our Lord and Saviour.