Know that an understanding of the fifty following articles must be based upon three things—the necessary (_wajib_), the impossible (_mustahil_), and the possible (_ja’iz_). The necessary is that the non-existence of which cannot be apprehended by the intellect (_aql_), that is, the intellect cannot affirm its non-existence, as boundary to a body (_jirm_), _i.e._, its taking up a certain measure of space (_faragh_). An example of a body is a tree or a stone. Then, whenever a person says to you, that a tree, for example, does not take up room (_mahall_) in the earth, your intellect cannot affirm that, for its taking up room is a necessary thing, the absence of which your intellect cannot affirm. The impossible is that the existence of which cannot be apprehended; that is, the intellect cannot affirm its existence. Then, whenever anyone says that such a body is bare of motion and rest at the same time, your intellect cannot affirm that, because being bare of motion and rest at the same time is an impossibility, the occurrence and existence of which the intellect cannot affirm, and whenever it is said that weakness (_ajz_) is impossible in God, the meaning is that the occurrence or existence of weakness in God is unthinkable. So, too, with the other impossibilities. And the possible is that the existence of which at one time, and the non-existence at another, the intellect can affirm, as the existence of a child of Zayd’s. When, then, someone says that Zayd has a child, your intellect acknowledges the possibility of the truth of that; and whenever he says that Zayd has no child, your intellect acknowledges the possibility of the truth of that. So the existence and the non-existence of a child of Zayd is possible; the intellect can believe in its existence or in its non-existence. And whenever it is said that God’s sustaining Zayd with a _dinar_ is a possibility, the meaning is that the intellect assents to the existence of that sustaining (_rizq_) at one time and to its non-existence at another.