The Supreme “I” principle; Mahatattva; Universal Mind—these are one and the same, expressed differently.
The Supreme “I” principle is next to the ‘Supreme-I’. The “Supreme-I” in this context is Purush, the Spirit Self. The Universal Mind is the Mind of the Spirit Self. Mahatattva is the first expression of the union of Purush and Prakriti.
From the perspective of the Self (Purush), the “Supreme-I” is Mahapurush, the Supreme Self. The Self and the Supreme Self, in this context, are the Sprit Self and the Supreme Spirit. The “spirit” is the Life Force inherent in Atman and Paramatman.
In the context of Purush and Mahapurush, Atman and Paramatman are the Self and the Supreme Self. The union of the Self and the Supreme Self can only be manifested by the Self. Paramatman (the Supreme Self) can only be realized by the Self as Purush, the Spirit Self.
The living self (Jivatman), the Spirit Self embodied in ego, intellect, mind, senses, and (optionally) the gross physical body, MUST realize its essence (Spirit Self) to be free from the false identification with the “mind’-body apparatus. (In this context, the “mind” refers to the fourfold inner organ, Antahkaranachautushtaya.)
Since the body is an extension of the mind, the real work is in the realm of the mind. This “mind” is the individualized mind and not the Universal Mind. The individualized mind is the Universal Mind circumscribed by ego. It is the result of the devolution of the living self during the process of the evolution of Prakriti (resulting from the union of Purush and Prakriti). The union of Purush and Prakriti is the basis of Ignorance (Avidya). Since the individualized mind is the product of Ignorance, the individualized mind is inherently ignorant.
The individualized mind is dissolved with the Wisdom of Consciousness. The true test of the presence of Wisdom is the absence of ego (false identification and the false pride associated with it). In other words, when wisdom is truly applied ego is removed and ignorance of our True Nature is eradicated. When this happens, the living self (Jivatman) is established in the Universal Mind.
Now begins the deeper spiritual work. The living self is now embodied in the Cosmic Ego since it is identified with the Universal Mind. The process of dissolving this subtle ego continues until the living self fully realizes its True Nature as the Spirit Self, Purush. Ultimately, all Ignorance is completely dissolved as Purush is united with Mahapurush, and the union of Atman and Paramatman is subsequently experienced as the state of Liberation (Moksha). In This, all that remains is the “Supreme-I.”