The Holy Grail symbolizes the senses of a human being which when purified through the powers of intelligence.

The eye is purified and made clear by the inner activity of the Ego-self working from Cosmic Realms of Being downwards into the physical form.

Then, and only then can the eye know the truth about itself and see upwards to the light that is looking for it.

This is the forming of the union of the soul to cosmic being and the path of truth