The terminology used by the ancient sages of the Vedic period was intended to convey, through symbolic language, a process whereby the human seeker would be able to prepare himself to receive the higher force and consciousness of Sat-Chit-Ananda and thereby transform his life in the world. Sri Aurobindo elsewhere goes into this subject at great length. Here he briefly explains:
“If we can break down the veil of the intellectual, emotional, sensational mind which our ordinary existence has built between us and the Divine, we can then take up through the Truth-mind all our mental, vital and physical experience and offer it up to the spiritual–this was the secret or mystic sense of the old Vedic “sacrifice”–to be converted into the terms of the infinite truth of Sachchidananda, and we can receive the powers and illuminations of the infinite Existence in forms of a divine knowledge, will and delight to be imposed on our mentality, vitality, physical existence till the lower is transformed into the perfect vessel of the higher. This was the double Vedic movement of the descent and birth of the gods in the human creature and the ascent of the human powers that struggle towards the divine knowledge, power and delight and climb into the godheads, the result of which was the possession of the One, the Infinite, the beatific existence, the union with God, the Immortality. By possession of this ideal plane we break down entirely the opposition of the lower and the higher existence, the false gulf created by the Ignorance between the finite and the Infinite, God and Nature, the One and the Many, open the gates of the Divine, fulfil the individual in the complete harmony of the cosmic consciousness and realise in the cosmic being the epiphany of the transcendent Sachchidananda.”
This interchange and relation can take place through an intermediate plane of existence that acts to translate and convert the knowledge, power and delight of the higher planes of unity into the forms that manifest in the lower planes of mind-life-body. “The link between the spiritual and the lower planes of the mental being is that which is called in the old Vedantic phraseology the vijnana and which we may term the Truth-plane or the ideal mind or supermind where the One and the Many meet and our being is freely open to the revealing light of the divine Truth and the inspiration of the divine Will and Knowledge.” It is at this level that the apparent contradictions of the multiplicity are resolved and harmonized into their inherent Oneness, while the particular meaning and purpose of the individual forms is maintained and recognized. Oneness thus does not imply the abolition of all differentiation of forms, forces and beings; rather, that each of these are recognized as elements that are One with each other yet which are part of an interplay that maintains its harmony even in the widest diversity. The One and the Many are two views of the same Reality and are thus capable of being reconciled by the supramental or truth-mind of this mediating plane of awareness.
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 15, The Cosmic Consciousness, pp. 399-400