Physical powers and intellectual attainments are not sufficient for the advancement of the world of humanity – we also need assistance from the divine Father

The world of humanity cannot advance through mere physical powers and intellectual attainments; nay, rather, the Holy Spirit is essential. The divine Father must assist the human world to attain maturity. The body of man is in need of physical and mental energy but his spirit requires the life and fortification of the Holy Spirit. Without its protection and quickening the human world would be extinguished. His Holiness Jesus Christ declared, "Let the dead bury their dead." He also said, "That which is born of the flesh is flesh, and that which is born of the spirit is spirit." It is evident therefore according to His Holiness that the human spirit which is not fortified by the presence of the Holy Spirit is dead and in need of resurrection by that divine power; otherwise, though materially advanced to high degrees man cannot attain full and complete progress. (Abdu'l-Baha, The Promulgation of Universal Peace, p. 181)