Existence is of two kinds: One is the existence of God which is beyond the comprehension of man. He, the Invisible, the Lofty and the Incomprehensible, is preceded by no cause but rather is the originator of the Cause of Causes. He, the Ancient, has had no beginning and is the All-Independent. The second kind of existence is the human existence. It is a common existence, comprehensible to the human mind, is not ancient, is dependent and has a cause to it. The mortal substance does not become eternal and vice-versa; the human kind does not become a Creator and vice-versa. The transformation of the innate substance is impossible. “In the world of existence, that which is comprehensible, is in three stages of mortality: the first stage is the mineral world, next the vegetable world, and in the latter the mineral world does exist but has 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: it has the faculties of hearing and of sight. In the human world the characteristics of the mineral, vegetable and animal world are found and in addition those of the human kind are existing. That is the intellectual characteristics, which discovers the realities of things and comprehends the all-important fact.
(Shoghi Effendi, Lights of Guidance, p. 503)