Since the Self is considered to be immutable, and outside the changes of Nature, we actually have two questions to resolve here. If the Self is not subject to change, it obviously cannot itself become subject to time, space and circumstance, i.e. the processes of rebirth and karma, birth, life and death. The Self stands outside of this process. The question then arises, what is it that actually becomes subjected to the process of rebirth and karma, and how does it differ from the immutable Self on one side, and the individual ego-personality on the other.
Sri Aurobindo discusses these questions: “We have in fact an immutable Self, a real Person, lord of this ever-changing personality which, again, assumes every-changing bodies, but the real Self knows itself always as above the mutation, watches and enjoys it, but is not involved in it. Through what does it enjoy the changes and feel them to be its own, even while knowing itself to be unaffected by them? The mind and ego-sense are only inferior instruments; there must be some more essential form of itself which the Real Man puts forth, puts in front of itself, as it were, and at the back of the changings to support and mirror them without being actually changed by them. This more essential form is or seems to be in man the mental being or mental person which the Upanishads speak of as the mental leader of the life and body, manomayah prana-sarira-neta. It is that which maintains the ego-sense as a function in the mind and enables us to have the firm conception of continuous identity in Time as opposed to the timeless identity of the Self.”