A primary difference identified by Sri Aurobindo between the supramental consciousness and the normal human mentality is the experience of oneness in an infinite consciousness. A human individual with an evolved rational awareness may accept the intellectual conception that all existence is One. He may even, with further development, intuit a sense of oneness, or a vastness of infinity. This remains an experience of division and fragmentation and does not carry the real internalized sense and experience of true oneness, which is the character of the supramental awareness.
Sri Aurobindo describes the supramental experience: “it is infinite consciousness and all that is conscious and acts and moves is seen, felt, received, known, lived in as self-experience and energy of the one being; it is infinite Ananda and all that feels and is felt is seen and felt and known, received and lived in as forms of the one Ananda. Everything else is only manifestation and circumstance of this one truth of our existence. This is no longer merely the seeing or knowing, but the very condition of the self in all and all in the self, God in all and all in God and all seen as God, and that condition is now not a thing offered to the reflecting spiritualised mind but held and lived by an integral, always present, always active realisation in the supramental nature.”
This experience changes the nature of thought, will and impulse as well: “There is thought here and will and sensation and everything that belongs to our nature, but it is transfigured and elevated into a higher consciousness. All thought is here seen and experienced as a luminous body of substance, a luminous movement of force, a luminous wave of Ananda of the being; it is not an idea in the void air of mind, but experienced in the reality and as the light of a reality of the infinite being. The will and impulsions are similarly experienced as a real power and substance of the Sat, the Chit, the Ananda of the Ishwara. All the spiritualised sensation and emotion are experienced as pure moulds of the consciousness and Ananda. The physical being itself is experienced as a conscious form and the vital being as an outpouring of the power and possession of the life of the spirit.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 21, The Gradations of the Supermind, pp. 792-793