What does the term greater is he that's in me than he that's in the world?

Answer 1

This phrase comes from the first letter of John (a disciple of Jesus who also wrote the 4th gospel, not John the baptist). He wrote to Christian believers in the first century, some time after Jesus' death and resurection. It wasn't addressed to christians in any one place, and would probably been read out to many different congregations after it had been hand copied.

The context from chapter 4 of 5, of the phrase is:

1Dear friends, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world. 2This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God, 3but every spirit that does not acknowledge Jesus is not from God. This is the spirit of the antichrist, which you have heard is coming and even now is already in the world.

4You, dear children, are from God and have overcome them, because the one who is in you is greater than the one who is in the world. 5They are from the world and therefore speak from the viewpoint of the world, and the world listens to them. 6We are from God, and whoever knows God listens to us; but whoever is not from God does not listen to us. This is how we recognize the Spirit[a] of truth and the spirit of falsehood.

John is contrasting spirits from God and spirits from the antichrist. Believers have invited God's Holy Spirit into their lives, to guide, strengthen them. It is this that is greater than the spirit of the world, symbolic of power-structures of the time, (Roman, local and religious rulers), that opposed the early church, which must have seemed weak and small in those early days. John wishes to encourage, and embolden the believers to share their faith.