IF JESUS had felt the need to attend a course on motivational speaking, the Gospels might now look different. This Gospel is larded with downbeat language: suffering, rejected, killed, deny, cross, lose, forfeit, ashamed, adulterous, sinful. Not the kind of positivity, you might think, needed to make 21st-century disciples.

But positivity is worth anything only when it bears some relationship to reality. The future, which Jesus sees more clearly than his disciples, is full of “darkness and cruel habitations”, as the Psalmist puts it (74.21 in the 1662 Psalter). Despite all his marvellous teachings, healings, and transformations, there are still elements of hostility and risk, suffering and death, which the disciples evidently have no wish to think about and prefer to ignore.

Only Peter objects to the darksome import of this teaching. He is rebuked for doing so, in the strongest terms imaginable. Jesus chooses not to empathise with the place of fear from which Peter is speaking, but to condemn Peter’s assumption and presumption.

Coming from Jesus, there can be few rebukes more painful than “Get thee behind me, Satan!” (8.33 AV). Satan’s name has been mentioned before in Mark’s Gospel; so even non-Jewish Christians knew it. But this is its final appearance. Satan instigated Jesus’s temptations in the wilderness (1.13). Jesus later used his name to teach about good and evil (3.23-26). In the fourth chapter, the parable of the sower provided an opportunity for Jesus to clarify Satan’s nature: he is the being who tries to lure believers away from their true allegiance and identity (4.15).

Satan’s last appearance in Mark — in this passage — is still as a tempter. But this time, the tempter wears a human face — specifically, the face of human friendship. Decades of special effects and CGI in film-making have made it easy for us to picture people being possessed by alien identities, or fluctuating between good and evil. It is not difficult to picture Satan inhabiting Peter’s person, and speaking with Peter’s voice. Indeed, it may be too easy to picture; for we have to wonder whether Jesus is really suggesting that Peter is demon-possessed. After all, it is a very extreme form of the influence of evil. Perhaps Jesus means no more than that Peter is echoing Satan’s first effort at tempting him.

This is the first time in scripture that a human being has been identified with Satan. That fact confirms the sharpness of Jesus’s rebuke, and also its strength. Peter has put the suggestion to him that he should rethink his message. But Peter is not acting alone: he is the spokesman for the whole group of disciples. We know this because of the way Jesus replies: “Turning and looking at his disciples, he rebuked Peter.”

Any entity that has both an individual and a group nature, which is both one and many, can be divine, as is the body of Christ (1 Corinthians 10.16). Or it can be demonic, as in the case of Jesus’s encounter with the demon that calls itself/themselves “Legion: for we are many” (Mark 5.9). Here, the command to Peter certainly applies to his fellow disciples, too.

“Get thee behind me, Satan!” is a saying that is familiar to plenty of people who never go to church or open a Bible. They learn what it means from seeing how it is used: one person tempts another to do something that would be better not done. By highlighting the true nature of the action being suggested, the exclamation helps the person being tempted to turn from succumbing to that temptation.

It is important to remember this background, and not just take the command in isolation; for it could be misconstrued. When Jesus says “Get behind me,” the Greek makes it clear that he is not saying, “Fall in behind me and follow me.” The idea is much closer to “Get out of my sight!”

Rebuke and criticism are tricky tools when you need to persuade your hearers to do what you want. Once again, the Lord fails the motivational-speaker test. He also fails the test of the demagogue; for demagogues will promise anything to keep their listeners onside, regardless of whether it can really be delivered. Here is proof, if we need it, that we can endure a message of suffering, and even the Lord’s rebuke, because he teaches “as one having authority” (1.22).