How does Chapter 17 use the analogy of the swan and milk to explain the ideal spiritual choice?

Chapter 17 employs a powerful analogy to illustrate the choice between the spiritual path (Shreya) and the worldly path (Preya). It states that just as milk and water can be mixed together, Shreya and Preya are blended in human life. However, a mythical swan, or 'Maral,' is said to be able to drink only the pure milk from the mixture, leaving the water behind. In the same way, this chapter advises that courageous, intelligent, and wise individuals should act like the swan. They must learn to discriminate and cling only to Shreya (the milk of wisdom and salvation) while completely turning away from and rejecting Preya (the water of worldly distractions).