There are all kinds of tales about ghosts, devils, witches,vampires; and not a few persons have claimed to have had various experiences with such creatures. Of the several cases that have come to my attention, most of the persons involved suffered from overly strong and diseased imaginations. One of them, a woman, had chanced to read a book about vampires, and her imaginations were so vivid that she believed one of them was sucking her blood away each night.Whenever she visited me she became well; but when the idea of the nightly presence of a vampire was so strong in her that after a time she would become ill again. She died prematurely, by her own thoughts.
In the sixteenth century, belief in witchcraft was widespread, and hundreds of persons suspected of being witches were falsely accused of being in league with the devil and were put to death. Joan of Arc was burnt at the stake as one be witched. Even Jesus Christ, who was healing the sick and doing only good, was accused of being in touch with Beelzebub. I t is true that at various times evil spirits in possessed persons recognized Jesus and spoken to him, saying,”Let us alone; what have we do with thee, thou Jesus of Nazareth? art thou come to destroy us? I know thee who thou art: the Holy one of God.” Jesus himself spoke of Satan and of evil spirits, which he exercised from many persons, in one case casting the evil spirits in to the bodies of a herd of swine.
There is another world, the astral, hidden behind this universe. Its inhabitants are garbed in an astral form made of light. Lacking a physical body, they are “ghosts”, invisible to us. Ordinarily they are confined to their own sphere, just as we are limited to our own physical world. If it were a simple matter for the ill- intentioned among astral beings to penetrate the earth plane and hurt us, we would be living in terror all the time. There is enough horror already on this earth of ours. Are not millions of deadly germs floating around? Certainly God would not add the interference of spooks to our sufferings?
There are, however , a few astral beings known as “tramp souls.” They are earthbound because of strong attachments to the world, and are desirous of entering a physical form for sense enjoyments. Such beings are usually unseen, and they have no power to affect the ordinary person. Tramp souls do occasionally succeed in entering and taking possession of somebody’s body, mind, but only when such a person is mentally unstable or has weakened his mind by keeping it often blank or unthinking. It is like leaving a car unlocked with the key in the ignition ; Some vagrant may get in and drive off. Tramp souls want a free ride in someone else’s physical body vehicle— anyone’s — having having lost their own that they were so attached to. It was in such cases of possession that Jesus exorcised the vagrant spirits. Tramp souls cannot stand the high vibration of spiritual thoughts and consciousness. Sincere seekers after God who practice scientific methods of prayer and meditation need never fear such beings. God is the spirit of all spirits. No harm from negative spirits can come to one whose thoughts are on God.
— By Sri Sri Paramahansa Yogananda from Man’s Eternal Quest