  This imaginary self, usually conceived in substantial terms as an unchanging reality behind the changing phenomenal world, is in effect the root cause of the pervasive ignorance which afflicts the human condition. From a metaphysical point of view, however, the not-self doctrine extends beyond the domain of subjective experience, to characterize all phenomena. Indeed, it is not just persons that are said to be selfless but all the elements of existence as well. To appreciate the uniqueness of the Buddhist not-self doctrine scholars sometimes contrast it with the two most common alternatives: eternalism and annihilationism (or physicalism). The eternalist, usually the Upaniṣadic philosopher, claims that the innermost part of ourselves, the subtle and abiding self, sometimes equated with pure consciousness, exists for all eternity even as the ordinary person undergoes constant change, ultimately resulting in his or her demise. At the opposite end of the spectrum we find the physicalist who sees human nature as contingent and finite.  The Buddhist perspective, called the ‘middle path between extremes’ or simply the ‘middle way’ (madhyamā-pratipad) offers a very different account of human existence: what we routinely call ego, self, soul, individual personality, are merely conventional terms that do not apply to anything real.