The self is to be recognised as the only eternal and all pervading consciousness on which the entire universe with all its infinite form and variety is manifest. The Upanishads know that the jivatma is sure to miss this aspect of his own self when he is immersed in the world of joy and sorrow and is engaged in daily activities of the world. Hence they repeatedly exhort the jivatma to reflect on his inner eternal reality as against the external and ephemeral contexts to which he is constantly exposed, pointed out Sri R. Rajagopala Sarma in a discourse.
The self is always non-dual. But when it is manifest in embodied form, it reveals itself in two ways, as the individual existential reality and also as the cosmic principle. When associated with an individual body the self is called the jiva and is in micro form; but when it is manifest as the collective body it is called Iswara and is in macro form. Both the micro and the macro forms are said to have three types of sarira, the gross or sthula sarira, the subtle or the sukshma sarira and the causal body, the karana sarira. But the self is distinct from all the three bodies which are categorised as the non-self or anatma. Their nature consists in unreality, inertness, and misery.
It then follows that the self is not the five kosas that envelop it, the annamaya, pranamaya, manomaya, vijnanamaya, and anandamaya kosas. It is of the essence of existence, knowledge and bliss. This truth can be surmised by discriminatory analysis of the waking, dream and deep sleep states which every one experiences. It will be seen that in all the states, the self remains a witness. The experience of the deep sleep state when recalled by anyone is seen to be beyond any association with the senses, mind and intellect, etc.