Acharya Prashant addresses a question regarding the difference between the brain and the mind, and the concept of memories from past lives. He explains that we do not carry any memories from our personal past lives. The memories that our bodies, cells, and DNA carry are the collective memory of all humankind and the entire journey of evolution. The notion of a personal past life is a projection of the ego, which identifies with the current body, name, and circumstances, and extends this sense of individuality into the past. He states that we have an infinite number of past lives, not a particular one, comparing it to a tree or a wave where everything comes from everything else. The individuality we believe in is a myth, and the ego's desire for private property extends to wanting a private past life. Further, Acharya Prashant distinguishes between the brain and the mind. The brain is a physical fact that exists irrespective of one's thoughts or state of consciousness. The mind, on the other hand, is a concept—a flexible, fluid entity that exists only in activity, such as thoughts, feelings, and impulses. The mind can come and go and is intrinsically linked to the 'I' or ego. He describes the mind as having an inner conflict: it wants to come to an end, yet it also wants to exist to witness its own end, which he calls a foolish and unwise desire. The mind must be counseled through right thought, or 'Atma-vichar'. Acharya Prashant elaborates that thought is both the lock and the key; it is the prison but also the means of liberation. The goal is not a thoughtless state achieved by randomly dropping thoughts, which would only make one unthinking. Instead, the aim is the fulfillment of thought, a state where thought is no longer needed because it has served its purpose. This is achieved by using sharp, penetrating, and inward-looking thought to investigate the nature of the self, its attachments, and its self-defeating ways. The mind, which seeks its missing half in the external world, must be guided by thought to understand its own tendencies and conflicts.