According to the bible, there CANNOT be 'ghosts'...spiritual parts of persons now deceased...because whatever people see or think they see...are ACTIVE...ON THE EARTH.
(Ecclesiastes 9:5-6) For the living are conscious that they will die; but as for the dead, they are conscious of nothing at all, neither do they anymore have wages, because the remembrance of them has been forgotten. 6 Also, their love and their hate and their jealousy have already perished, and they have no portion anymore to time indefinite in anything that has to be done under the sun.
If the dead are NOT CONSCIOUS , then they cannot be active.
So the only answer to any paranormal activity is demon activity...'
(Revelation 12:12) On this account be glad, YOU heavens and YOU who reside in them! Woe for the earth and for the sea, because the Devil has come down to YOU, having great anger, knowing he has a short period of time.”
And his demons came with him...They are stuck on the earth right up till Armageddon.
And causing us lots of grief...wars, anger, road rage etc etc.