What is Shelley's idea of spiritual beauty as expressed in "Hymn to Intellectual Beauty"?

Shelley contends that spiritual beauty gives “grace and truth to life’s unquiet dream" while nourishing intellectual thought. If man retains this beauty in his heart, he can attain immortality. 
Spiritual beauty is a power in man that can replace traditional religious worship with man's potential to attain perfection. Rather than seeking spiritual beauty in traditional religion, Shelley maintains that spiritual beauty is to be found in a power in man's intellectual thought that extends beyond the senses. Thus, it contains ideals toward which people should strive in their efforts to attain this perfection. In stanza 3, for instance, Shelley writes,

Thy [Spirit of Beauty] light alone. . . Gives grace and truth to life's unquiet dreams.

In stanza 4, Shelley mentions human beings' responses to this Spirit of Beauty, responses of thought which serve to elevate the intellect:

Love, Hope, and Self-esteem, like clouds depart   And come, for some uncertain moments lent.Man were immortal, and omnipotent. 

The abstract, intellectual ideal which is the Spirit of Beauty is attained through man's contemplation of nature and the exercise and development of intellectual thought, all of which enable man to perceive and reach perfection.