The Mahavakya "I AM THAT" (that = SELF).
In these statement, THAT is always the SELF. But to make this statement as non-dual. 'I' should be THAT (SELF). But than, do i know "WHO AM I'. No. So to question 'who am i' is perfectly right.. the origin of the thought or the source of the thought (i.e. 'who am i' is the SELF. The absence or the source of EGO is the SELF. - Sri Ramana Maharshi (40 verses on Truth).
From Sri Ramana Maharshi's 40 Verses on Truth