There was widespread belief in ghosts in Polynesian culture, some of which persists today. After death, a person's ghost would normally travel to the sky world or the underworld, but some could stay on earth. In many Polynesian legends, ghosts were often actively involved in the affairs of the living. Ghosts might also cause sickness or even invade the body of ordinary people, to be driven out through strong medicines.
In the reconstructed Proto-Polynesian language, the word "*qaitu" refers to a ghost, the spirit of a dead person, while the word "*tupuqa" has a broader meaning including all supernatural beings. Some of the ancient Māui legends that are common throughout the Polynesian islands include the idea of a double soul inhabiting the body. One was the soul which never forsakes man, and the other the soul that could be separated or charmed away from the body by incantations was the "hau".
In some societies, the tattoo marks on the Polynesian's face indicated their cult. A spiral symbol meant that the man favoured the sky world, but before ascending there on a whirlwind his ghost had to travel to his people's homeland, situated in the navel of the world. Different markings indicated that the ghost chose to live in the underworld. The Hawaiians believed in "aumakua", ghosts who did not go down into Po, the land of King Milu. These ghosts remained in the land of the living, guarding their former families.
All Polynesian societies have many stories of ghosts or spirits who played a role in their traditional legends. William Drake Westervelt collected and published eighteen of them in Hawaiian Legends of Ghosts and Ghost-Gods (1915). The legend of Pele, the Hawaiian goddess of volcanic fire, relates how she fell in love with a man, but found that he had died. She found his ghost as a thin presence in a cave, and with great difficulty used her magical powers to restore him to life. He was destroyed again, but his ghost was once more found, this time in the form of a bird flitting over the waters, and once more restored to life.
Another Hawaiian legend tells of a young man who fell into the hands of the priests of a high temple who captured and sacrificed him to their god, and then planned to treat his bones dishonorably. The young man's ghost revealed the situation to his father through a dream, and aided his father to retrieve the bones through great exertions and to place them in his own secret burial cave. The ghost of the young man was then able to joyfully go down to the spirit world.
Ghost sickness in Polynesia takes two forms: possession and bizarre behavior, where the victim often talks with the voice of a dead person, and retarded healing caused by a ghost or evil spirit. The patient is treated with strong-smelling plants such as beach pea, island rue or ti plant (Cordyline fruticosa), and in the case of possession through reasoning with the ghost.
Of his 1892 Tahitian painting Manao Tupapau, Paul Gauguin said "according to Tahitian beliefs, the title Manao Tupapau has a double meaning . . . either she thinks of the ghost or the ghost thinks of her".
Robert Louis Stevenson wrote about Polynesian beliefs and customs, including the belief in ghosts, in his last collection of stories, Island Nights' Entertainments. He wrote the book on Samoa in 1893 in a realistic style that was not well received by the critics, but the stories which dealt with false and real supernatural events are now considered among his best .