How does Chapter 14 explain the concepts of oneness and duality, and what is the path to realizing non-duality?

According to the philosophical teachings in Chapter 14, the intellect that establishes duality, or manifoldness, is described as pure ignorance and is the cause of the endless cycle of birth and death. The path to realizing non-duality, or oneness, is achieved through the Guru's teachings, which lead to the purification of the mind. As this chapter details, one must turn away from ignorance and surrender to the Essence that is the same in one's own body as it is in the entire universe. True non-duality is attained when there is not even a trace of difference left in the mind, recognizing that everything, from Brahma to a blade of grass, is pervaded by Brahman.