Tat is ‘That’, ‘tvam’ is ‘this’. What is ‘That’? What is distant is referred to as ‘that’ and what is near is called ‘this’. Our sense determine what is near and what is far. The physical body in close proximity to the senses was called ‘this’ by the rishis. The principle beyond the reach of the senses is ‘That’, the Atma…. Thus, we have the Vedic injunction – Tat Tvam Asi – That Thou Art.
(Summer Showers 1991, Pg 32)