Life Force

The Life Force is an occult substance stored and used by living beings, generally considered to be the realm of mysticism instead of science in modern times. It is commonly treated as a synonym for the soul. Some theories describe multiple types of soul that handle successively higher forms of existence; corresponding to modern ideas of a life/sentience/sapience hierarchy, so the soul inherent to every living creature can fit the definition of a life force. If possession of any soul requires all souls of a lower type, this would explain the idea that artificial intelligences lack a soul, being deprived of the most basic measure of life force, although the modern conception of AI is much newer than stories where life forces are directly used to create artificial intelligence. That said, life force often exists independently of living beings, following an ecological cycle like life's other materials where it is released and concentrates at different levels in different locations, benefitting the ones that are better at accumulating it. An abundance of life force can be the source of other supernatural properties, but many supernatural beings will still have power over it if this isn't the case.