What philosophical insights does Chapter 14 offer regarding duality (manifoldness) and oneness (non-duality)?

Chapter 14 delves into the philosophical concepts of oneness and duality. It teaches that the intellect establishing duality, or seeing differences, is pure ignorance and leads to the endless cycle of birth and death. The chapter clarifies that turning away from this ignorance is the path to attaining oneness. True non-duality requires the complete absence of any perceived difference in the mind. According to the teachings in this chapter, the Guru's guidance purifies the mind, allowing one to realize their true nature. The ultimate truth presented is that the same Essence in one's body is present in the entire universe, and everything from Brahma down to a blade of grass is pervaded by Brahman.