This is one of the most famous quotes in the Bible. Thousands of words have been written on it.

John 1

1In the beginning was the Word, and the Word was with God, and the Word was God. 2He was in the beginning with God. 3All things came into being through him, and without him not one thing came into being. What has come into being 4in him was life, and the life was the light of all people. 5The light shines in the darkness, and the darkness did not overcome it.

via Daily Lectionary Readings — Devotions and Readings — Ministries & Programs — GAMC.

I will not consider the metaphors of logos — the word, and light driving out darkness. There are two other challenges.

The first is that this person was God, and with God, and was one with God. (There is nothing new here — in Genesis we are told that a man will leave his parents, and he and his wife will become one).

The second is in the following verses (a) that this person became a human (b) that the people rejected him and (c) that this writer witnessed this, and the life he witnessed was a true rellection of w-ho and what God is.

Thus, for a Christian, Jesus is their theology.