What does it mean that the kingdom of God is spiritual?

The nature of the kingdom of God is often misperceived as a political or physical reign. However, Jesus teaches through His walking on water and His refusal to be made king during His ministry that the kingdom is fundamentally spiritual. It is not characterized by external force but exists within the hearts of believers (Luke 17:20-21). This spiritual kingdom transcends geographical boundaries and is realized through the transformative work of the Holy Spirit in the lives of individuals. The disciples’ struggle to understand this truth highlights humanity's inclination to seek worldly measures of success rather than grasping the true essence of God’s reign in their lives.