Man has a complex multi-faceted nature that can be understood through various models. He is described as having a spiritual essence or higher self (Atma) and a soul (Buddhi) that together form the immortal individuality. Man also has a mind (Manas) that connects him to desires (Kama), vital life force (Prana), an astral body (Linga-Sharira), and a physical form (Sthula-Sharira). Understanding these different aspects of human nature helps explain how man evolves spiritually through reincarnation and the relationship between his higher and lower selves.