Can you explain the teachings on duality and non-duality presented in Chapter 14?

Chapter 14 offers a deep dive into the philosophical concepts of oneness (non-duality) and manifoldness (duality). It teaches that the intellect establishing duality, or seeing differences, is a form of pure ignorance that traps one in the cycle of birth and death. The path to liberation involves turning away from this ignorance to attain oneness. According to the chapter, this is achieved through the Guru's teachings, which lead to the purification of the mind. The ultimate truth is that everything, 'from Brahma down to a blade of grass,' is pervaded by Brahman, the Supreme Reality. True understanding comes from recognizing this universal essence and surrendering to it.