Despite the fact that Jesus’ gave His disciples authority to expel demons (see Mark 6:7), their attempt to dislodge a demon from a young boy met with total failure. The father of the demonized boy pinpointed the cause: “they did not have the power/strength” (Mark 9:18; ίσχύω). They had Jesus’ authority, but no power. They lacked the supernatural power required to expel the demo. Divine authority without power equals powerlessness; the disciples might well have used spit-wads.