Acharya Prashant explains that the physical body and the brain are biological systems that function without inherent spiritual unrest. The sense of 'I' or the ego (Aham) is the entity that experiences restlessness and identifies itself with the body. This identification occurs because the ego feels incomplete and seeks fulfillment or profit through the body. Consequently, human consciousness becomes infected by the ego, leading individuals to perceive everything from a self-centered perspective. Every thought and observation becomes subjective, where one cannot view the world without silently linking it back to themselves and their opinions.