I think they believed in ghost....
Mark 6:49 but when they saw him walking on the sea they thought it was a
ghost, and cried out,
Strongs
5326 phantasm....an apparition, ghost, spirit, phantom.
Matt 14:26 But when the disciples saw him walking on the sea, they were terrified, and said, “It is a
ghost!” and they cried out in fear.
Strongs
5326 again.
Luke 24:37 But they were startled and frightened, thinking they had seen a
spirit. (some translations say ghost.)
4151. pneuma
Was this Samuel or a demon?
1 Sam 28:
11Then the woman said, “Whom shall I bring up for you?” He said, “Bring up Samuel for me.”
12When the woman saw Samuel, she cried out with a loud voice. And the woman said to Saul, “Why have you deceived me? You are Saul.”
13The king said to her, “Do not be afraid. What do you see?” And the woman said to Saul, “I see a god coming up out of the earth.”
14He said to her, “What is his appearance?” And she said, “An old man is coming up, and he is wrapped in a robe.” And Saul knew that it was Samuel, and he bowed with his face to the ground and paid homage.