Just as a lamp illumines a jar or a pot

so also the Atman illumines the mind and the sense organs, etc.

These material-objects by themselves cannot illumine themselves because they are inert.

A lighted-lamp does not need another lamp to illumine its light.

So too, Atman which is Knowledge itself needs no other knowledge to know it.

- Sri Adi Shankaracharya. Atma Bodha.

Verses 28 &29.