What philosophical ideas about duality and the role of a Guru are introduced at the beginning of Chapter 12?

The start of Chapter 12 of the Sai Satcharitra introduces key philosophical concepts centered on the Guru's role in spiritual liberation. The Guru, personified by Sai, is described as the embodiment of "Truth, Consciousness, and Bliss" who stills the "waves of worldly existence." The central teaching highlighted is that through the knowledge of non-duality, the Guru removes the "obsession with duality" from a person's mind, even if they are dull-witted. The Guru is metaphorically described as the "Agastya for the ocean of worldly existence" and the "sun for the darkness of ignorance," signifying their power to help devotees overcome life's struggles and achieve enlightenment.