Acts 19:15

And the evil spirit answered and said The most ancient texts add unto them. They had taken upon them to use the name of Jesus, but the result was far contrary to their wishes and intentions. "Evil spirit" is used for the man in whom the spirit was. Cp. Mark 3:11.

Jesus I know, and Paul I know The verbs are not the same, though it is hardly possible in a translation to mark the difference. In the first there seems to be intended a recognition and admission of power, in the other a recognition of an appointed ministry thereof. The spirit speaking through the man would intimate: I recognise that Jesus has power over evil spirits, and I know that Paul is a true servant of Jesus, through whom Jesus manifests His power.

but who are ye? Who are not followers of Jesus, and so are mere pretenders in the use of His name.