In the Gospel, Mark gives us an account of Jesus teaching in the synagogue in Capernaum. Mark does not tell us what Jesus teaches, but does tell us that he does so with authority. Not entirely surprising, because Mark is often more concerned with what Jesus does rather than with what he says. What was important for Mark here was not so much what Jesus actually taught, but that he did it with authority. Apparently, Jesus made a deep impression on those in the synagogue, because, unlike the scribes, he taught them with authority.
There are, of course, different kinds of authority. Teaching with authority could simply mean speaking well or speaking with self-confidence, like the good speaker who wins the debating competition. The speaker's argument doesn't matter so much: the matter under consideration is how well he or she presents the argument. We can presume that there was something more to Jesus's authority than debating skills.
Another kind authority comes from representing people. Members of Parliament have been elected to represent, in some sense, their constituents. We don't send delegates to Parliament who are directed by their constituents on every issue, but send as our MPs people whom we want to represent us. A MP's authority comes from those they represent. Again this is not the nature of Jesus's authority; it does not come through representing people. The people often get things wrong and Jesus cannot be seen as a representative of that. Jesus calls his followers rather than his followers calling him.
It is the unclean spirit in the gospel reading who points to where Jesus's authority does come from. The unclean Spirit says to Jesus, 'Have you come to destroy us? I know who you are: the Holy One of God.' We tend to think that a man with an unclean spirit means an evil man, and it could mean that here, but it could mean a man who was a bit mad or simply somebody who was ill. Ordinary illnesses could be seen as being the work of unclean spirits.
In any case, it means that the man with the unclean spirit was not as he should be. He was not the human being that God intended him to be. Jesus was able to recognise that. Some may not be impressed by that, but I think that it is something that everybody fails to do at least some of the time. We admire some people we shouldn't. We admire their achievements, but if we think about it, we realise they are not something to admire. In the end, cornering huge amounts of power and wealth does nobody any good. Even considering ourselves, we will take pride in things we actually should be sorry for.
The authority Jesus possessed came from being able to see through all human misperceptions and malaise to identify where the truth of the matter lay. In every case he was right. Whether it be malice or illness, Jesus saw that the issue was a lack of humanity. In the man with an unclean spirit, Jesus saw a lack of humanity. The man was not as God intended.
In the end, Jesus's authority came from being right: right about the human condition. The unclean spirit knew this ability could only come from God, who alone knows what human beings are really can be.
Speaking the truth gave Jesus his authority. The unclean spirit recognised that divine authority and knew that it was subject to that authority. There is no room here for a dualism between good and evil. God and goodness are not in some cosmic battle with evil spirits where we eagerly await unknowable outcome. Evil spirits are subject to divine authority. In the Gospel, the evil spirit 'went out' of the man at Jesus's command.
Jesus's authority came from God: knowing and proclaiming the divine truth. It gave Jesus authority over evil spirits. The people then knew that Jesus taught with authority.
When we recognise truth and justice we see God. Just as people in the Gospel saw God and authority in the truth and rightness of what Jesus said. Ultimately, Jesus's authority denies space for evil and reaffirms the goodness of humanity and creation.