This is the post-Halloween question I was waiting for! It’s a good question, especially for those old enough to remember when the Trinity was defined as “Father, Son, and Holy Ghost.” First, the word ghost comes from the German Geist, which means “spirit.” So there is less difference between these terms than we normally ascribe. Our modern idea of ghosts, however, is so shaped by horror films and the occult that I can’t say simply: Yes, Catholicism admits the reality of ghosts. Let me take a longer route to the answer.
Catholicism teaches that we are both body and soul, or as Saint Paul says (using the Greek for these words), flesh and spirit. The soul is a “substantial and spiritual principle endowed with immortality” according to the Catholic Encyclopedia. It’s substantial because it has elements of being, such as potency, stability, and the capacity to be modified. It’s spiritual in that it is immaterial and has intelligence and free will—irrespective of its relationship to a physical body. When we die, the soul separates from the body, to be reunited “at the end of the ages.”
Jesuit John Hardon in his Modern Catholic Dictionary notes that God may and does permit the souls of the dead to appear before the living when it’s suitable for our salvation. The lives of the saints are full of such apparitions. Church teaching, based in biblical tradition, warns against trying to conjure or control such spirits as occult practices routinely do. That means just say no to Ouija boards, séances, mediums, automatic writing, tarot cards, or other supernatural methods for obtaining information.
Seeking the aid of powers other than God is a deterrent to faith, does not lead to good, and can lead to harm. That is the Catholic position on the supernatural in general. Note: It is not a refutation of the existence of supernatural things, angels, demons, and “ghosts” included. In fact, because exorcism is still on the books in Catholic teaching, it would confirm rather than deny the reality of the spiritual world.
But for heaven’s sake, none of this should make you scared! Catholics believe that God alone is sovereign, and there is no power or principality equal to divine authority—Satan included. Lost souls aren’t wandering around aimlessly or even purposefully to get you. All created things must answer to God, just like you and me. The Ghost you’re most likely to engage is a Holy one.
• Deuteronomy 18:9-14; 1 Samuel 28:4-25; 2 Kings 21:6; Isaiah 3:1-3; Micah 5:11; Acts 7:51-53; 13:6-12; 16:16-24; 19:13-20
• "I believe in life everlasting," Catechism of the Catholic Church
• Our Lady of the Lost and Found: A Novel of Mary, Faith, and Friendship by Diane Schoemperlen (Penguin Books, 2001)
• Apparitions of Modern Saints by Patricia Treece (Charis Books, 2001)