FEAR

As per the ancient TAO tradition it is stated that the 5 main emotions of the person are connected with the 5 vital organs of the body. Any disturbance in the organ would effect the connected emotion and the eruption of any emotion would effect the organ. 
The very simple example is
When a person is in deep fear, he/she develops dark circles, the area below the eyes are connected with KIDNEY as per Nadi(energy) shashtra.

SPIRITS were HUMAN

As the law of thermodynamics say "Energy can neither be created not be destroyed but can be changed from one form to another" and the same was proved by Einstein by his world famous formula E=mc2. 
If the above law stay true then as we all know that what ever is there in or outside of us is ENERGY. The Human Body is made up of energy and even the paranormal world would also be a composition of energy.
So the big question comes.. if we apply the law of thermodynamics to the principle of DEATH what would we get... quite interesting...
The Human Body is a form of energy and when DEATH is applied to this body a transformation takes place on the energy level.

Body is transformed into Spirit

Thus if we reverse engineer SPIRIT we get HUMAN.

The other big question that comes now is that do we fear fellow human being? If NO then why do we need to fear the SPIRIT WORLD.

Question yourself and get back with your doubts.