LIGHT

To show the invincibility of Jesus, 1John 1:1 combines the Genesis record (…that which was from the beginning, 1Jn1:1a), the Mt. Sinai/Mt Horeb record (…which we have heard[1Jn1:1b,Deut 6:4], and the Gospel record (…that which we have looked upon…the Word of Life…the life that was manifested [1Jn1:1c] to construct his definition of Light(1Jn1:1:5].
John is saying that because the “laws of nature” in Genesis align with the morally contrasting laws of God [Exod, Deut], this overwhelming truth cannot be overtaken by men who speak otherwise [Jn1:5]. It shows the preeminence of Christ [Col1:18]