Man has two powers; and his development, two aspects. One power is connected with the material world, and by it he is capable of material advancement. The other power is spiritual, and through its development his inner, potential nature is awakened. These powers are like two wings. Both must be developed, for flight is impossible with one wing. Praise be to God! Material advancement has been evident in the world, but there is need of spiritual advancement in like proportion. We must strive unceasingly and without rest to accomplish the development of the spiritual nature in man, and endeavor with tireless energy to advance humanity toward the nobility of its true and intended station. For the body of man is accidental; it is of no importance. The time of its disintegration will inevitably come. But the spirit of man is essential and, therefore, eternal. It is a divine bounty. It is the effulgence of the Sun of Reality and, therefore, of greater importance than the physical body.
- ‘Abdu’l-Baha (From a talk, 25 April, 1912, Washington, D.C.; ‘The Promulgation of Universal Peace: Talks Delivered by 'Abdu'l-Bahá during His Visit to the United States and Canada in 1912’)