Sakshi (witness)
In Hindu philosophy, Sakshi, also Sākṣī, "witness," is the 'pure awareness' that witnesses all things and events. It witnesses all thoughts, words and deeds without affecting them or being affected by them. It is beyond time and space and the triad of experiencer, experiencing and experienced. Sakshi or Shiva, along with Shakti, represents Brahman, the totality itself in its most fundamental state, the almighty and all-pervasive, revealed in ancient Hindu philosophical texts.
Etymology and meaning
Sākṣī means 'observer', 'Witness-Self' or the 'Supreme Being'. It is the Atman, the unchangeable eternal Reality, Pure Consciousness, self-luminous and never itself an object of observation. It is the timeless Being that witnesses the ceaseless flow and change in the world of thought and things.It lends its shine to the "ego" part of the subtle body, which consists of the everchanging Mind, the decision-making Intellect, the Memory and the Illusory Ego.
Upanishads
The word साक्षी is used in the following verse from Shvetashvatara Upanishad,The Varaha Upanishad refers to one of the seven Bhumikas which is of the form of pranava. It has four parts due to the difference of sthula, sukshama, bija and sakshi. Their corresponding avasthas are – waking, dreaming, dream-less sleep, and turiya. The state of consciousness identified with the Sakshi essence is 'turiya'.
Panini
Panini states that the term indicates a direct seer or eyewitness. Sakshi means Ishvara, the चेता, the sole Self-consciousness, who is the witness of all, who gives consciousness to every human being, thereby making each rational and discriminatory.Vedanta
Vedanta speaks of mind, or antahkarana, and matter as the subtle and gross forms of one and the same reality. The field of mind involves the duality of subject and object, the seer and the seen, the observer and the observed ; this duality is overcome in the field of pure Consciousness. Such knowledge, says Sankara, does not destroy or create, it only illumines. According to the Drg-drshya-Viveka:Swami Sarvapriyananda explains it thus: