Souls and Mana

In this world of fantasy, the energies of life and magic have become intertwined, granting the people and creatures of this world access to fantastical abilities. This magic flows through all living things, and manifests itself within the body in the shape of a Soul.

 
This Soul serves as the body's connection to the world around it, and acts as a means for channeling Mana throughout the body. Mana, being the raw magic energy that makes up the universe. 

When a Soul leaves the body, it does not take with it any of the person's memories, but it does take the emotional experiences that developed because of them. Thus a Soul outside a body is a creature of pure emotion, acting not out of logic or reasoning, but how their emotional reaction to a situation would dictate.
It cannot speak, or project its thoughts mentally, however a soul can project its emotions outward to attempt to interact with the living world

Because of a Souls intimate relationship to a person's emotions, these emotions naturally have an effect on that person's relationship to the magic around them. Those with more Spirit than others tend to have a stronger connection to their emotions, and thus a stronger access to the magic around them as well. 

If a body finds itself alive and without a Soul, that person can still act and think normally but with two exceptions;

They will no longer experience any emotion, and attempt to use rationalize any action they take like a cold, calculating machine, and will always act in the manner that best serves for their of survival.

They will no longer be able to use magic or any magic tool requiring mana to operate, and their Spirit Score becomes 0.