How do we know the Kingdom of God is not of this world?

Jesus' proclamation in John 18:36 affirms that His kingdom operates on a different plane than earthly kingdoms. It is a kingdom characterized not by physical territory or political power, but by a sovereign rule in the hearts of believers. This internal quality of the Kingdom is echoed in John 3:3, where Jesus tells Nicodemus that no one can see the kingdom unless they are born again. The Kingdom is both a present reality and a future hope, as Paul explains in 1 Corinthians 15:50 when he asserts, 'Flesh and blood cannot inherit the kingdom of God.' The nature of this kingdom, therefore, emphasizes spiritual rebirth and eternal life rather than temporal authority.