In the 18th chapter of the  Ilahiyyat of the Daneshname-ye ‘Ala’i, the Shaykh al-Ra’is writes,

The being of that entity which has being, is either necessary (wajib) in itself due to its own nature, or it is not necessary. The being of that which is not necessary in itself is either an impossibility (mumtani’) or a contingency (mumkin). Whatever is impossible in itself can never [become] existent (mawjud) as we indicated previously. Consequently, it must be contingent due to itself and necessary due to the condition (shart) that its cause exists, whereas it is an impossiblity due to the condition that its cause does not exist. One factor is its being, and another distinct factor is the condition of the  the existence or the non-existence of a cause. When one considers its being-qua-being without any other conditions, it is neither a necessity nor an impossibility. When one considers that determined cause which is the condition for realizing its cause, it becomes a necessity, whereas it becomes an impossibility if one considers as its cause the condition of the non-realization (na-hasil) of its cause. Hence, if one considers number without regard to any conditions which are usually associated with it, its nature cannot be an impossibility, for as such it would never exist. But, if one regards the state of the number four which results from two times two, the result must be a necessity, for its non-realization as four is an impossibility. Hence, any existing entity, for which existence is not intrinsically necessary, is contingent it itself. Therefore, this entity is a contingent being in itself and a non-contingent being (namumkin) with regard to something else (ghair). Its existence is not yet realized in such a manner that it must exist due to that reason. Since becoming an existent is a contingency, and since a contingency in itself is never realized because it has not come from a cause, it is necessary, therefore, that the contingency be realized by means of a cause so that it may become necessary to that cause as an existent. And that entity, or that existent, is of such a nature that its union with its cause is completed and that all its conditions are fulfilled when it becomes an existent. Furthermore, a cause becomes a cause due to (‘illa) its acting. Hence, a cause becomes a cause due to action when it must be active so that an effect may necessarily result from it.