What is a Ghost?
Ghosts, according to legend, a dead person's soul or spirit that assumes a physical appearance. Most scientists believe that reports of ghosts are caused by hallucinations or some other kind of optical illusion. The power of suggestion combined with dim light or shadows may be enough to create the illusion of a ghost. In some cases nervous disorders, alcoholism, the effects of drugs, and unusually vivid and realistic dreams may convince someone that he is actually seeing or hearing a ghost.
Some ghosts are thought to have the ability to become invisible, walk through walls, and perform other supernatural feats. Ghosts who haunt the living are believed to be seeking revenge for the manner of their death or burial or for some other wrong that they suffered in life. The ghosts of people who have been murdered are supposed to be especially common. Outstanding fictional examples of ghosts occur in several of Shakespeare's plays, including Hamlet, Julius Caesar, Macbeth, and Richard III.
The belief in ghosts has existed in most parts of the world from early times to the present. It is probably based on the age-old belief in angels, demons, and spirits and on man's refusal to accept the finality of death. Throughout history primitive peoples have used drugs, fasting, dancing, and other methods to conjure ghosts and so to maintain contact with the supernatural.
Although modern psychologists are aware of the delusive powers of self-hypnosis and hallucination, some scientists admit that there are ghostlike experiences that cannot be scientifically explained. Societies for psychical research have been established in New York City and London to investigate reports of ghosts and to discover the actual basis for such reports.