In ordinary cases of error (bhrama), the knowledge of reality proceeds in two stages. First, the erroneous superimposition must be removed by separating the real object from the falsely attributed one. Second, the substratum itself must be positively known. For example, in the classic rope-snake illusion, it is not sufficient merely to know, “This is not a snake.” One must further know, “This is a rope.” Otherwise, other possibilities—such as its being a crack in the ground (bhūchidra), a garland (mālā), or some other object—remain open. Thus, complete knowledge requires both the negation of error and the ascertainment of the actual object.
This twofold process is necessary because, in the sphere of empirical experience (loka-vyavahāra), both the appearance and the reality are objective entities that can be perceived and distinguished through the senses and the mind.
The knowledge of the Ātman, however, is fundamentally different. The reality being sought is not an external object but one’s own self-revealing existence. Since the Ātman can never become an object of experience, there is no second object that has to be positively cognized after the negation of error. The only error consists in the superimposition of the non-self (anātman) upon the Self. Therefore, once this superimposition is completely removed through discrimination (ātma-anātma-viveka), nothing further remains to be known. The Self is ever self-established (svataḥ-siddha); it does not require an additional act of cognition. Hence, in Self-knowledge, the complete discrimination between Ātman and anātman is itself exhaustive of liberation-producing knowledge.