The soul, accoring to many religious and philosophical traditions, is the self-aware essence unique to a particular living being. In these traditions the soul is thought to incorporate the inner essence of each living being, and to be the true basis for sapience, rather than the brain or any other material or natural part of the biological organism. Some religions and philosophies on the other hand believe in the soul having a material component, and some have even tried to establish the weight of the soul. Souls are usually considered to be immortal and to exist prior to incarnation.