A turning point in the evolution of Shūnyam occurs when Uddalaka’s distinguished disciple Yājñavalkya, in the Bṛhadāraṇyaka Upaniṣad, lays out a simple algorithmic rule to get to Brahman, to Brahman.
The exact word used is Ātman, a synonymous appellation and related to the English word ‘Animate’: to come alive, [the Latin Anima Mundi]. Ātman is simply: ‘That which animates Life’.
As is uniformly true of all radically revealing insights it was ridiculously simple to lay-out [and not so simple to effect]. The formula is: ‘It is not this! It is not this!’ [Neti, Neti].
What is ‘It’? And why is the Rule repeated twice? The common interpretation is that this was a sweeping rejection of ‘World as Object’ and a relapse to an ‘Inner Self’ in line with the terminus of the Chandogya Upanishad.
In the subsequent centuries, the linear application of the Rule reduces the Teaching to unverifiable dogma, superstitious cant and petitionary prayer. The regression of the Tradition begins.
The Rule is not the revelation: ‘I am not this potted plant’. The Rule is about the claimant, the speaker with the revelation: ‘I am not this potted plant’.
The ‘It’ refers to the Subject making the claim. The rule properly interpreted is a self-scuttling circular loop. ‘The Backward Step’ designed to scuttle the presumed Subject and not a forward sweep for locating a new Object [such as an imagined Brahman].
Used as linear unfolding Yājñavalkya’s Rule has no natural convergence and will enter into an insidious spin. No amount of negating will lead to convergence unless the negating finally turns in on itself. And the reel will spin forever if you don’t at some point see that you are part of the movie.
The formula completes, the circle is rounded only when the aim, act and agent of negation are themselves consumed in full self-scuttle. It is a meta-statement; an assertion about an assertion. Yājñavalkya’s Rule, properly rounded becomes: ‘It is not this! It is not: ‘It is not this!’.
When properly rounded Yājñavalkya’s Rule becomes the first formulated Self-Negating Expression and the earliest definition for the Symbol ‘0’.
Two thousand years later variants of the Rule rebirth in world philosophies as the ‘Via Negativa‘, later still as the Docta Ignoranta, and in-turn terminate in a variety of short-stops to ‘True Nothing’.