To exist, to have a hold-in this dimension, the energy that is a soul needs to latch on to something that already exists here, namely a body. Bodies are physical entities, they have brains and neurons shooting information all over the place, they have the ability to think and feel. How much of that is the brain? How much of that is the soul? The soul can't exist in this dimension without a body. But, does that mean a body can't exist without a soul? Well, that's what we had to find out, that was the first step...