The Kain Upanishad says, kain aishitam patati, prayishitam manah. The word the razor's edge is used in the Upanishads to describe the delicate, difficult nature of this knowledge. Even the highest spiritual texts nervously refer to you as 'not this' or 'what it is not' So Pushpalanta here says, Atat Vyavrityaayam, Chakita Mabhirhat Te Shruti Rapishuti Upanishads. They designate, they talk about the ultimate reality, Brahman, you, in which way? Nithi Nithi, not this, not this,. Not this,