This topic has been discussed here a number of times and I’ve been on BOTH sides of the discussion convinced of my answer. Now, I’m a bit confused.
On the one hand, there is no place in Catholic doctrine for a belief in ghosts. When we die, we go to either heaven, hell or purgatory. Those in hell are trapped there forever and have no capability to wander the earth. Those in purgatory are also trapped there being purged of the stains their sins and waiting for their release. Those in heaven are happier beyond their wildest dreams (* " … eye has not seen and ear has not heard [1 Corinthians 2:9] … "* ) and have no reason to be wandering around the earth.
Thus, the logical conclusion is that ghosts are really demons pretending to be our departed loved ones for some evil purpose.
On the other hand, the bible is also filled with examples of ghosts. Saul was able to summon Samuel’s ghost through the power of a witch. A number of times Jesus assured the apostles that He was NOT a ghosts (when He walked on water, when He appeared to them after His death, etc.). If there are no such things as ghosts, there would have been no reason for Jesus to tell them that He wasn’t one.
So, what is the conclusion? Ghosts … do they exist?