From 'Naan Yaar'

Sri Ramana Maharshi

When will the realization of the Self be gained?

When the world which is what-is-seen has been removed, there will be realization of the Self which is the seer.

Will there not be realization even while the world is there (taken as real)?

There will not be.

Why?

The seer and the object seen are like the rope and the snake. Just as the knowledge of the rope which is the substrate will not arise unless the false knowledge of the illusory serpent goes, so the realization of the Self which is the substrate will not be gained unless the belief that the world is real is removed.