From the beginning to the end of his life man passes through certain periods, or stages, each of which is marked by certain conditions peculiar to itself. For instance, during the period of childhood his conditions and requirements are characteristic of that degree of intelligence and capacity. After a time he enters the period of youth, in which his former conditions and needs are superseded by new requirements applicable to the advance in his degree. His faculties of observation are broadened and deepened; his intelligent capacities are trained and awakened; the limitations and environment of childhood no longer restrict his energies and accomplishments. At last he passes out of the period of youth and enters the stage, or station, of maturity, which necessitates another transformation and corresponding advance in his sphere of life activity. New powers and perceptions clothe him, teaching and training commensurate with his progression occupy his mind, special bounties and bestowals descend in proportion to his increased capacities, and his former period of youth and its conditions will no longer satisfy his matured view and vision.
`Abdu'l-Bahá: The Promulgation of Universal Peace