Pretty much lot of things that traditionally are attributed to the soul (such as memory, thoughts, and persona) can be explained by the physical brain. Likewise, life can be explained by chemical reactions in humans' flesh and blood bodies. With death simply being the body losing its functions like a machine that is unrepairable (as opposed to a soul leaving the body). In such cases, what exactly is the human soul and how does it differ from the brain and rest of the body? Also, how would reincarnation work given the old memories are inside the brain of the former person? Or does the soul have a copy of the memories that gets passed down to the reincarnation?