36: Kingdom is not of this world, and is not from this world. Its source and its substance are God himself. This is why our battle is not against flesh and blood (Ephesians 6)
37: Yet again we see that one of the main purposes Jesus came to earth was to "bear witness" to the truth. But then he makes the outrageous claim that "Everyone who is of truth listens to my voice." As Ravi Zacharias said, Jesus is saying that how you react to his words tells more about your own truthfulness than it does about Jesus. This is either utterly arrogant or absolutely true.
38: Noble attempt at a worthy rebuttal to Christ (Nietzsche loved this phrase), but it rings hollow to us readers. Pilate doesn't realize that the Truth is standing right before him. The better, more correct question would have been "Who is truth?"
For John, Jesus is up for verdict for the reader as well, and Pilate's verdict that he found no guilt invites the reader to come to the same conclusion.
Do I listen to His voice - am I "of the truth"? Do I bear witness to the Truth? Do I view truth as cut-and-dry abstract facts about reality, or as being found only in the person Jesus Christ, Son of God?