Chapter 6 · Verse 9

एक एवाद्वयो ब्रह्म नान्यत् किञ्चिदस्ति वै

eka evādvayo brahma nānyat kiñcid asti vai

Only one without division is Brahman; nothing else exists at all. In chapter 6 this is explored as the very nature of existence. Non-duality here is not a denial of the world but its re-cognition as Brahman. The point is not to claim that forms fail to appear, but to see that they appear within the one, like waves that never ceased to be water.