"... man must pass from degree to degree of progressive unfoldment until perfection is attained."

"It is evident, therefore, that man is in need of divine education and inspiration, that the spirit and bounties of God are essential to his development. That is to say, the teachings of Christ and the Prophets are necessary for his education and guidance. Why? Because They are the divine Gardeners Who till the earth of human hearts and minds. They educate man, uproot the weeds, burn the thorns and remodel the waste places into gardens and orchards where fruitful trees grow. The wisdom and purpose of Their training is that man must pass from degree to degree of progressive unfoldment until perfection is attained. For instance, if a man should live his entire life in one city, he cannot gain a knowledge of the whole world. To become perfectly informed he must visit other cities, see the mountains and valleys, cross the rivers and traverse the plains. In other words, without progressive and universal education perfection will not be attained."

`Abdu'l-Bahá, The Promulgation of Universal Peace, p. 295
29 August 1912 - Talk at Home of Madame Morey - Malden, Massachusetts