What are unclean spirits?

Question 8037.

The phrase unclean spirits runs right through the Synoptic Gospels and the book of Acts, and most readers slide past it as a synonym for demons. It is a synonym, but it is not an accidental one. The word chosen tells us how Scripture wants us to think about these beings, and the emphasis is not the one we expect.

We tend to categorise the demonic in terms of power. The Gospel writers reached for a word about defilement. That difference is worth sitting with, because it changes what we think the danger actually is.

The word itself

The Greek is akathartos, meaning impure or unclean, and it is the standard word used in the Greek Old Testament for ceremonial defilement. It describes what may not come near holy things, what must be washed, what excludes a person from the assembly.

When Mark writes about unclean spirits he is using the vocabulary of the tabernacle rather than the vocabulary of the battlefield. Mark 1:23 introduces a man in the synagogue with an unclean spirit, which is a deliberate collision of terms. Something that could not lawfully enter the courts of the LORD was sitting in the congregation.

So the name is a moral description rather than a measure of strength. Unclean spirits are defiling before they are dangerous, and Scripture wants us to feel the offence of their presence before we start calculating their capabilities.

Where unclean spirits appear in Scripture

Mark uses it more than anyone, some eleven times, and Luke follows closely. Matthew has it, and Acts records Philip’s ministry in Samaria where unclean spirits came out of many who had them, crying with a loud voice.

Revelation picks up the phrase near the end, describing three unclean spirits like frogs coming out of the mouth of the dragon, the beast and the false prophet. Even in apocalyptic imagery the word retains its moral force. These are not simply hostile beings; they are polluting ones.

John’s Gospel, interestingly, does not use the phrase at all and records no exorcisms, which is one of those features of the fourth Gospel that reminds us each writer had his own purpose and selected accordingly.

Why unclean rather than powerful

Think about what the word would have meant to a first-century Jewish reader. Uncleanness was not about hygiene. It was about fitness to approach God. A person who became unclean could not worship until the matter was dealt with, and the whole sacrificial system existed to address that gap.

To call these beings unclean spirits is therefore to say something devastating about them. They are permanently unfit for the presence of God, not through misfortune but through rebellion, and there is no offering that covers them. Hebrews 2:16 says it is not angels that Jesus helps but the offspring of Abraham.

It also says something about what they do to a person. Their aim is not simply to harm but to defile, to drag a human being made in the image of God into what is unfit for Him. That is why the Gospels so often connect them with tombs, with self-harm, with nakedness and with isolation.

What they recognised

One of the most striking features of the accounts is that unclean spirits consistently identified Jesus correctly when almost nobody else did. In Mark 1:24 the spirit cries out, “What have you to do with us, Jesus of Nazareth? Have you come to destroy us? I know who you are, the Holy One of God.”

Read that alongside the disciples asking one another who this could be that even the wind and sea obey Him, and the contrast is uncomfortable. The theology of the demons was better than the theology of the disciples. James says as much when he writes that even the demons believe, and shudder.

The title they used is worth noticing too. They called Him the Holy One, which is exactly the opposite of what they were. Unclean spirits confronted by absolute holiness knew instantly what they were looking at.

How Jesus dealt with them

Without ceremony. There are no incantations, no ritual objects, no lengthy procedures. He speaks and they go. Mark 1:27 records the crowd’s amazement: “What is this? A new teaching with authority! He commands even the unclean spirits, and they obey him.”

He also silenced them. Repeatedly He forbade unclean spirits to speak, even when what they said was accurate. Truth spoken by the wrong mouth is not helpful, and Jesus wanted no testimony from that quarter. There is a lesson there about the sources we allow to speak for us.

And He delegated the same authority. Matthew 10:1 says He called His twelve disciples and gave them authority over unclean spirits, to cast them out. The seventy-two returned rejoicing that even the demons were subject to them in His name, and He redirected their joy to the fact that their names were written in heaven.

The empty house

Matthew 12:43 contains one of the most sobering things Jesus said on this subject. When the unclean spirit has gone out of a person, it passes through waterless places seeking rest and finds none. Then it says, I will return to my house from which I came, and finding it empty, swept and put in order, it brings seven other spirits more evil than itself.

The warning is aimed squarely at deliverance without conversion. A cleared life that remains empty is an invitation. The remedy for unclean spirits is not a vacancy but an occupant, and the occupant Scripture offers is the Holy Spirit Himself.

This is why I have no interest in exorcism as a stand-alone ministry. The goal is never the departure of a spirit. The goal is the salvation of a person, and anything short of that leaves them worse off than before.

Cleanness and the gospel

The whole theme comes together beautifully in the ministry of Jesus. He touched a leper and was not defiled; the leper was cleansed. He allowed a woman with a discharge of blood to touch His garment and power went out from Him. Uncleanness, which had always flowed one way, suddenly began flowing the other.

That is the answer to unclean spirits in a sentence. Holiness in the person of Jesus is not fragile. It is contagious. 1 John 1:7 says the blood of Jesus his Son cleanses us from all sin, and the verb is present tense and continuous.

Hebrews 9:14 makes the connection explicit, saying the blood of Christ will purify our conscience from dead works to serve the living God. The conscience is exactly where uncleanness is felt most keenly, and it is exactly where the remedy is applied.

What this means for believers

A Christian is indwelt by the Spirit of God and cannot be inhabited by an unclean spirit. 1 Corinthians 6:19 calls the body a temple of the Holy Spirit, and the imagery of a temple is precisely the imagery of a place from which uncleanness is excluded.

That does not make us untouchable. We can be tempted, harassed and accused from outside, and the enemy will work at our thinking, our appetites and our relationships. But the difference between assault and occupation is not a technicality. See also where demons live and whether demons are the same as fallen angels.

Keeping proportion

It is possible to become so interested in unclean spirits that they colonise your imagination without ever coming near your soul. I have watched it happen. People start seeing them everywhere, and the Christian life shrinks into a permanent state of alert.

The Gospels do not read like that. Jesus deals with unclean spirits as they arise, decisively and briefly, and then gets on with preaching, teaching and healing. They occupy a small proportion of the narrative and almost none of His conversation. That proportion is worth imitating.

The same proportion shows up in the letters. Paul writes thirteen letters covering church order, marriage, money, work, suffering, resurrection and a dozen other subjects, and the demonic occupies a handful of paragraphs. If our teaching diet is weighted differently from the New Testament, something has gone askew.

So, now what?

Take the word seriously. What Scripture warns us about is defilement, and defilement usually arrives quietly through what we watch, read, excuse and feed rather than through anything dramatic.

And take the remedy seriously too. There is a fountain opened for uncleanness and it has never yet run dry. If you feel soiled by something this week, the answer is not a technique but a bath, and the water is the blood of Jesus. Why carry what He offered to wash?

Holiness is not something we protect by keeping our distance. It is something we receive from the one who touched lepers and was never once contaminated by it.

“And they were all amazed, so that they questioned among themselves, saying, What is this? A new teaching with authority! He commands even the unclean spirits, and they obey him.”

Mark 1:27, ESV