What are the core philosophical concepts of Shreya and Preya as explained in Chapter 17?

Chapter 17 explains the concepts of Shreya (the Good/Path of Salvation) and Preya (the Pleasant/Path of Worldly Joy) as being of opposite natures, like light and darkness. Shreya is described as the form of discrimination and pure Knowledge (Vidya), while Preya is the form of ignorance (Avidya) and lack of discrimination. The chapter states that one whose mind runs toward Preya falls away from their true self-interest. While both paths are available, a wise person clings only to Shreya, turning away from Preya, much like a swan separates milk from water. The text emphasizes that choosing Shreya over Preya is the true purpose of human life.