What does Mark 9:23 mean?

Jesus' words have been translated several different ways. He may have been making an ironic rebuke to a father and a crowd who have placed their faith (and doubt) in the disciples instead of God. Or He may be saying, "As far as your words, 'if you can'…" to highlight what He is responding to.

The sentiment He quotes reflects the climate of the entire crowd. The father has a hard time believing Jesus can save his boy when His disciples can't, the scribes don't believe Jesus' power comes from God (Mark 3:22), and the disciples' limited faith isn't directed at God where it should be. Like in Nazareth, the collective lack of faith threatens to prevent the miracle (Mark 6:1–6).

Jesus isn't saying that we can accomplish anything we want if we have enough faith; this isn't an endorsement of the Word of Faith teachings. True faith doesn't presume that God will do what we want but that God can do what He wants (see: Mark 1:40–42). Jesus will expand this truth from healing to salvation when He tells the disciples that the rich can only be saved through God's power and not man's intent (Mark 10:25–27). If the scribes have been reiterating their accusation that Jesus' power comes from Satan (Mark 9:14), then Jesus is telling the father to choose whom he believes—Jesus or the scribes.