If this is the case, why does Paul cast out the demon if it is not actually telling a lie at the time? Or, why does the demon force the girl to identify Paul and Silas in this way? Perhaps Paul was not interested in having the spirit of Python as a witness. The true witness in Acts is the Holy Spirit. The demon may have identified Paul in this way in order to show its power over Paul, in the sense of “I know who you really are, etc.” In Luke 8:28 a demon identifies Jesus as the Most High God. In both cases the demon is attempting to express power over a potential exorcist.
The slave girl’s pronouncement is not a single occurrence, but rather an ongoing problem for Paul. It is as if this slave girl is following him around all day! Luke uses the verb διαπονέομαι (diaponeomai), “to be deeply distressed” or “to be greatly annoyed.” This is the same verb used earlier in Acts 4:2 to describe the feeling of the Sanhedrin over the preaching of the apostles (ie., that Jesus was raised from the dead), and it is the word found in LXX Gen 6:6 for God’s grief over the sin of the world prior to the flood. Paul is not merely annoyed, he is deeply distraught at the situation and casts out the demon without any ritual at all.
What is the point of this story? Keener suggests this story contributes to Luke’s overall theme that “nothing can hinder the Gospel” (3:2420). This includes a very powerful demonic spirit, the “most high god” and even the local political leaders in Philippi. Perhaps Luke includes the story to draw a literary parallel to Luke 8:26-33 where another demon identifies someone as the Most High God.