Krsna says that ahankara itiyam me bhinna prakrtir asta... Everything is finer. Just like the earth is grosser than the water. Water, finer. Earth you cannot move, but water can move. Therefore it is finer. And finer than the earth is the fire, and finer than the fire is air, and finer than the air is ether, and finer than the ether is the mind, and finer than the mind is intelligence, and finer than intelligence is my identity, ahankara. And finer than the ahankara is the soul. You have to study soul - finer, finer, finer, finer, finer.
Lecture on Bhagavad-gita 7.4, Vrindavana, August 10, 1974