Bahá’í World Faith—Selected Writings of Bahá’u’lláh and ‘Abdu’l-Bahá (‘Abdu’l-Bahá’s Section Only)

Know that nothing which exists remains in a state of repose, that is to say, all things are in motion. Everything is either growing or declining, all things are either coming from non-existence into being, or going from existence into non-existence. So this flower, this hyacinth, during a certain period of time was coming from the world of non-existence into being, and now it is going from being into non-existence. This state of motion is said to be essential—that is, natural; it cannot be separated from beings because it is their essential requirement, as it is the essential requirement of fire to burn.

Thus it is established that this movement is necessary to existence, which is either growing or declining. Now, as the spirit continues to exist after death, it necessarily progresses or declines: 331 and in the other world, to cease to progress is the same as to decline; but it never leaves its own condition, in which it continues to develop. For example, the reality of the spirit of Peter, however far it may progress, will not reach to the condition of the Reality of Christ; it progresses only in its own environment.

Look at this mineral: however far it may evolve, it only evolves in its own condition; you cannot bring the crystal to a state where it can attain to sight: this is impossible. So the moon which is in the heavens, however far it might evolve, could never become a luminous sun; but in its own condition it has apogee and perigee. However far the disciples might progress, they could never become Christ. It is true that coal could become a diamond, but both are in the mineral condition and their component elements are the same.