What is the principle of psychic fortune telling?

It depends on whether you believe it or not.

There is a more scientific explanation. Some people think that ghosts are brain waves formed after death, because brain waves will remain in the world after death. When people's brain waves are the same as or similar to those of ghosts, we can see the so-called ghosts. Further explanation, ghosts really exist, but only the residual brain waves lead to the existence of ghosts. The greater the grievances and emotions of ghosts before they die, the stronger the relative ghosts (brain waves), so the stronger the ghosts that human beings can see, and even the possibility of harming human beings. This is how these people explain' ghosts'. People who believe in this explanation usually don't believe in hell, heaven and Taoism.

But many people have another explanation for ghosts. This explanation is that the soul leaves the body after death, so this soul is the so-called ghost. They believe that the ghost can go through the solid and wait without touching the ground. These people usually believe that there is hell, there are three lives, and ghosts from the underworld will also appear at the Ghost Moon Festival. People can see these ghosts by accident. Some people think it is because they have done too many wrong things or hurt too many people. However, some people think that the above method is just a lie that China told children in ancient times. Those who can really see these ghosts are those who are born with special functions of yin and yang eyes. They believe that people with yin and yang eyes can see ghosts, hear ghosts and feel the existence of ghosts (some even believe that they can see ghosts by drawing tears from cows on their eyes). These people with yin and yang eyes usually play the roles of mediums, fortune tellers, etc., helping the dead to talk to his or her living people.

These are just some social and world phenomena. As for the existence of ghosts, this problem beyond science and convention is left to your own judgment. But so far, no.

Anyone can really prove that ghosts don't exist.