This essay explores the similarities in the thought of the Greek philosopher Parmenides (fifth century b.c.e .) and that of the Indian philosopher Śaṅkara (eighth to ninth centuries c.e .). Parmenides’ being is compared to the nonduality of Brahman and ātman, as defended by Sankara. The focus is especially on the methods used by both philosophers to help readers know nondual reality. First, they both make a distinction (krísis/viveka) between being (real, Self) and not-being (unreal, Non-self); and second, starting from this distinction, they both test, by means of negative dialectic, what, according to common sense, are the fundamental characteristics of reality.