[1] The Upanishads address two fundamental ideas – Brahman and the Atman; as a rule these terms are used synonymously, there is no difference between these two.
[3] The Vedas are part of oral tradition, therefore they are called Śruti (that which is heard), Upanishads, known as the Vedanta, are the destroyer of bondage.
The oneness of the Individual Self and the Universal Self (jīvātma paramātma aikyam) is Śrutisara, the ultimate purport of the Vedas.
Rishi Venobhargavah (Rig Veda IX.85.9) also speaks about the same knowledge of Oneness when he prays:- and tells us about the stars and celestial luminaries dotting the sky shining because of the light of the self-effulgent Brahman shining brightly revealing everything and providing strength and stability (अधिद्यामस्थात्), who is pure and the source of amrita (पीयूषं) desired by the learned people (नृचक्षसः), who is the giver of happiness and who is the deliverer being the only source of immortality.201-203[6] Vedantasara explains that the subject (visheya) is the identity of the individual self and Brahman, which is of the nature of Pure Intelligence (wherein all ideas of separation and variety are effaced) and is to be realized – सर्वे वेदा यत् पदमामनन्ति – That goal which all the Vedas declare (Katha Upanishad I.ii.15), and that the connection (sambandha) is the relation between that identity which is to be realized and the evidence of the Upanishads that establishes it, as between a thing to be known and that which tells of it.p.
While the Atman stays within the limits of the body, emotions and intellect, there cannot be any dissolution, any absolute unity (sarvarthā- aikyam) with Brahman; the soul is only the reflection of the higher ātman.