Based on the description in Chapter 48, what is the ultimate defining quality of a Sadguru that enables them to enlighten others?

The ultimate defining quality of a Sadguru, as detailed in Chapter 48 of the Shri Sai Satcharitra, is the possession of direct, full self-experience. The chapter emphasizes that vast verbal knowledge, the ability to explain scriptures, or prescribing mantras are insufficient. A person who lacks personal experience cannot impart it to a disciple. The text poses a rhetorical question: "One who does not have experience himself, what will he give to the disciple?" Therefore, as Chapter 48 clarifies, it is this "taste of experience," which only an experienced person can manifest, that grants a Sadguru the authority and capacity to truly enlighten their followers.