The first step in spiritual life is to understand, that we are not these bodies, but eternal spiritual souls trapped inside material bodies. In Bhagavad-gita Krishna tells Arjuna, that understanding this is not as hard as one would think. Krishna simply asks Arjuna to notice how the body keeps changing throughout life, from childhood, to youth, to old age, while at the same time the self remains the same. “I” am always the same unchanging “me.” Since “I” am always the same conscious person, while the body keeps changing, the self and the body must be two different things. According to Krishna in Bhagavad-gita (2.13):
“As the embodied soul continuously passes, in this body, from boyhood to youth to old age, the soul similarly passes into another body at death. A sober person is not bewildered by such a change.”
We are in other words referring to reincarnation, which means that the same person lives in different bodies at different times. This process is not only supported by Bhagavad-gita, but also by modern scientists who have studied phenomena such as near death experiences, and children who have memories from previous lives. One of such scientists is the Dutch doctor Pim van Lommel, who interviewed over 300 people who have experienced clinical death, and could explain how they had been conscious outside of their bodies. Another scientist, the Canadian psychiatrist Ian Stephenson, documented 3000 cases of children who remembered previous lives.
Reincarnation means, that we are eternal spiritual beings, moving in a cycle of birth and death. In this life I am a human being, but in the next life I may be a dog, a cow, a demigod, a bird, a plant, and so on. Now I may be Danish, but in my next life I may be born as a Swede, or a German, or an Indian. Maybe I am a man in this life, but in my next I may be born a woman, and so on.