When the official asked Jesus to heal his son, why did Jesus say, "Unless you see signs and wonders, you will not believe."? It doesn't seem to fit that Jesus said this to criticize the father who was seeking healing. Instead we see a clue in John 20:30-31, "Now Jesus did many other signs...these are written that you may believe that Jesus is the Christ, the son of God, and that by believing you may have life in his name."
Jesus' first sign at Cana in John was turning water into wine...and when it was his time, turning wine into blood. Jesus' second sign was healing the son of the official and giving him life...and when it was his time, healing our spiritual illness and raising us from death to life.
All around us are signs of death: illness, unrest, violence, strife and physical death. It is actually through these signs of death that Jesus is at work to destroy death and the devil. Jesus gives us signs of his life that we may believe, and have life in him.