What is the meaning behind the analogy of the stone and the gem in Chapter 19? How does it relate to a disciple's development?

The analogy of the stone and the gem, found in Chapter 19, illustrates that a Guru's guidance affects disciples differently based on their inherent spiritual readiness. The text explains that just as a whetstone polishes both a stone and a gem, a Guru's teachings are applied to all. However, the outcome varies; a stone simply becomes smooth, while a gem "becomes a brilliant jewel." This metaphor, as explained in Chapter 19, suggests that even with a powerful Guru, the disciple's own "wisdom," which includes "strong faith at the Guru’s feet and the strength of courage which is patience," is crucial for true transformation. The process is the same, but the disciple's innate quality determines the result.