A mediator is necessary between man and the Creator -- one who receives the full light of the Divine Splendor and radiates it over the human world, as the earth's atmosphere receives and diffuses the warmth of the sun's rays.
If we wish to pray, we must have some object on which to concentrate. If we turn to God, we must direct our hearts to a certain center. If man worships God otherwise than through His Manifestation, he must first form a conception of God, and that conception is created by his own mind. As the finite cannot comprehend the Infinite, so God is not to be comprehended in this fashion. That which man conceives with his own mind he comprehends. That which he can comprehend is not God. That conception of God which a man forms for himself is but a phantasm, an image, an imagination, an illusion. There is no connection between such a conception and the Supreme Being.
If a man wishes to know God, he must find Him in the perfect mirror, Christ or Bahá'u'lláh. In either of these mirrors he will see reflected the Sun of Divinity.
As we know the physical sun by its splendor, by its light and heat, so we know God, the Spiritual Sun, when He shines forth from the temple of Manifestation, by His attributes of perfection, by the beauty of His qualities and by the splendor of His light. (Words of ‘Abdu’l-Baha, from a talk to Mr. Percy Woodcock, 'Akká, 1909; quoted by Dr. John Esslemont in ‘Baha’u’llah and the New Era’)