Yoga, says the Patanjali Yoga Sutra, is the state of mind where all its movements are stopped. In that state what happens, the individual remains as the seer alone. The seer is the very Purusha or the truth itself. In that truth, there is no distinction between the knower, knowing and the known, says the Vivekachoodamani of Sri Adi Sankaracharya. What is left in the absence of the three factors? There is only a limitless reality that has no modifications or thoughts, feelings and emotions in it. It is alone and complete by itself. It is not broken into any parts. It is the form of consciousness. It is the supreme essence. The wise know it in this way, as their own self.
The self or the I, that we so often use to refer to ourselves, is not something that can be brushed aside or put away. Wherever we go, it is there—I am there. It cannot also be brought from somewhere and stocked or hoarded! That Self is beyond the grasp of the mind and speech. It cannot be measured with any yardstick—a scale, an inch tape, a thread or even time. It is without a beginning and an end. It is that Brahman, which is complete. It is the Self called I.
The Upanishads declare: Tat Twam Asi—That Thou Art. Tat is the supreme reality—Brahman. Twam is the jiva or the individual entity—you and me. Asi means are, am. That is you. While studying the statement and contemplating on it, the qualities of both are highly contradictory like the President and the Resident. Both are humans, but there are differences in them. While understanding this statement, it is important to take the implied meaning and not the literal meaning to arrive at the truth because their differences are like the sun and the glow worm, king and the servant, the well and the ocean, the smallest atom and the mount Meru.
So when Tatwamasi says You are God, the associative understanding of the body, mind, intellect, emotions and energies as you is the direct meaning.The implied meaning of You is that factor of existence—manifested as life—which is present everywhere in all the living beings and as mere existence in the non-living things. That is You, which is the same as the Supreme.
The difference between the individual and God is only the limiting adjunct called the Upadhi. While for Ishwara or the supreme ruler, Maya or the pure quality of knowledge is the limiting factor, for jiva, the Individual—the five sheaths of body, vital airs, mind, intellect and the innermost core experience of bliss–are the limitations.