The author distinguishes between writing about worldly gurus, multiple saints, and one's Sadguru. Can you elaborate on the spiritual hierarchy and ultimate goal presented in these distinctions?

In Chapter 0, the author presents a clear spiritual hierarchy regarding the service of writing biographies. At the base level is writing about worldly Gurus, which he deems a service limited by space and time, rooted in some self-interest, and not productive of eternal spiritual fruits. A step above is writing of many saints; this is a valid form of Guru service yielding spiritual fruit, but he calls it 'one-sided or partial' and insufficient for attaining the ultimate goal. The pinnacle of this service, which grants the 'fruit of salvation,' is writing the biography of one's own Sadguru. This act, when inspired and performed with pure devotion, becomes a complete spiritual practice that also involves regular personal study and encouraging others, thereby leading to the ultimate spiritual attainment.