Passage
He came as a witness, to bear witness about the Light, so that all might believe through him.
John 1:7 (LSB)
Nearby Context
John 1:5 And the Light shines in the darkness, and the darkness did not overtake it.
John 1:6 There was a man having been sent from God, whose name was John.
John 1:7 He came as a witness, to bear witness about the Light, so that all might believe through him.
John 1:8 He was not the Light, but he came to bear witness about the Light.
John 1:9 There was the true Light which, coming into the world, enlightens everyone.
Study Lenses
The verse centers on "light", "came", "witness", "bear", "might", "believe", and "through". It is saying that the verse draws attention to "light" and "came", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 6's "There was a man having been sent..." into verse 8's "He was not the Light but he...", so "light" and "came" belong inside that flow. In John context, the local focus is the identity of Jesus, new birth, eternal life, and belief and unbelief.
A plain takeaway is to answer the verse's own emphasis on "light" and "came" with trust shaped by these words, not by a vague optimism outside the passage.