Bhagavad Gita, Chapter 18, Verse 20

That by which the one indestructible Substance is seen in all beings, inseparate in the separated, know that knowledge to be Sâttvika.

Real unity is named here as what goodness actually sees, one reality underneath every visible difference.

This kind of knowledge doesn't deny real diversity, it recognizes something shared underneath it. Real insight, in this mode, moves toward connection rather than separation.