Bhagavad Gita, Chapter 14, Verse 11

When through every sense in this body, the light of intelligence shines, then it should be known that Sattva is predominant.

Real illumination is named here as the clearest sign that goodness is currently in charge.

Knowledge lighting up every gate of the body is offered as a concrete, observable marker of sattva at work. Real signs, not guesswork, are given for recognizing which force is active.