Bhagavad Gita · Chapter 2: The Path of Understanding
Bhagavad Gita 2.25
अव्यक्तोऽयमचिन्त्योऽयमविकार्योऽयमुच्यते ।
तस्मादेवं विदित्वैनं नानुशोचितुमर्हसि ॥
avyakto'yamacintyo'yamavikāryo'yamucyate | tasmādevaṃ viditvainaṃ nānuśocitumarhasi ||
It is said to be unmanifest, beyond thought, and unchanging. Knowing it to be so, you should not grieve.
Modern context
The self cannot be seen, cannot be pictured in thought, and does not change. Krishna is candid that what he is pointing to lies beyond the instruments we normally use to know things. It is not an object in our experience; it is the one who has the experience.