In the world of existence—that which is comprehensible—there are stages of mortality: the first stage is the mineral world, next is the vegetable world. In the latter world the mineral doth exist but with a distinctive feature which is the vegetable characteristic. Likewise in the animal world, the mineral and vegetable characteristics are present and in addition the characteristics of the animal world are to be found, which are the faculties of hearing and of sight. In the human world the characteristics of the mineral, vegetable and animal worlds are found and in addition that of the human kind, namely the intellectual characteristic, which discovereth the realities of things and comprehendeth universal principles.
- ‘Abdu’l-Baha (‘Selections from the Writings of ‘Abdu’l-Baha’)