What is the root cause of the cycle of birth and death (Samsara) as explained in these passages?

The primary cause of the perpetual cycle of worldly existence, or Samsara, is a fundamental ignorance regarding one's true nature. As detailed in Chapter 37, this cycle of death following birth and rebirth following death eternally pursues anyone who holds a knowledge of difference. This delusion is the belief that 'Parabrahman is different from me; I am not that, I am something else.' This mistaken perception of being separate from the ultimate reality, Brahman, is what subjects the soul to the endless wheel of Samsara.