Chapter 19 uses an analogy involving a stone and a gem being polished. What is the deeper meaning of this comparison in the context of a Guru and disciple?

The analogy of the stone and the gem in Chapter 19 serves as a sophisticated lesson on the receptivity of a disciple. The text explains that both a stone and a gem can be subjected to the same polishing process on a whetstone. However, the gem becomes a brilliant, sparkling jewel, while the stone only becomes smooth. This illustrates that while a Guru provides the same spiritual guidance and 'polishing' to all disciples, the final outcome depends on the disciple's inherent nature and readiness. As Chapter 19 implies, a disciple with the intrinsic qualities of a 'gem'—such as strong faith and patience—will absorb the teachings and shine with spiritual luster, whereas one who is like a 'stone' will not achieve the same transformation despite undergoing the same process.