How does Chapter 17 use the analogy of the swan with milk and water to illustrate spiritual discernment?

Chapter 17 employs a powerful analogy to explain the challenge of choosing the right spiritual path. It states that Shreya (the Good) and Preya (the Pleasant) are often blended together, just as milk can be mixed with water. The text then introduces the mythical swan (Maral), which is said to be able to drink only the pure milk from such a mixture, leaving the water behind. This imagery illustrates how courageous, intelligent, and wise individuals can discern and cling only to Shreya. In this way, Chapter 17 teaches that the true purpose of human life is to be like the swan, separating the spiritually nourishing from the worldly and distracting.