Samskara-saksat-karanat-purva-jati-jnanam. By bringing unconscious drives into conscious light one knows the existence of previous lives.
Yoga Sutras III:18
Upon dissolution of the body, the Self principle does not perish. The body is a manifestation of Self principle. The knowledge one has acquired and the character one has gained will accompany one into future lives. Higher future life depends on higher karmas of past and present. Birth and death merely mean union of individual self with a new organism and separation from the old organism. –Shri Brahmananda Sarasvati
‘Your everlasting soul has appeared and reappeared in different lives, bodies, and times. The Atman is the name for the soul in Sanskrit. It is the subtle or etheric body that resides within the physical body. It has moved through thousands of bodies, places, and times – even on other planets than Earth, and in other bodies than human. It is your True identity and it is immortal.’ Excerpt from September Focus by David Life