monidean proofs of the existence, unity and incorporeality of God and points out that they are not valid because in the first place they are based upon premises which Crescas has refuted, and secondly were the premises granted Maimonides's results do not follow from them.388 It remains then for Crescas to give his own views on this problem which, he says, the philosophers are unable to solve satisfactorily, and the Bible alone is to be relied upon. At the same time he does give a logical proof which in reality is not different from one of the proofs given by Maimonides himself. It is based upon the distinction insisted upon by Alfarabi and Avicenna between the "possible existent" and the "necessary existent." Whatever is an effect of a cause is in itself merely possible, and owes the necessity of its existence to its cause. Now, argues Crescas, whether the number of causes and effects is finite or infinite, there must be one cause of all of them which is not itself an effect. For if all things are effects they are "possible existents" as regards their own nature, and require a cause which will make them exist rather than not. This self-subsisting cause is God.389
He then endeavors to prove the unity of God in the two senses of the term; unity in the sense of simplicity, and unity in the sense of uniqueness. Unity as opposed to composition — the former sense of the term — is neither the same as the essence of a thing, nor is it an accident added to the essence. It cannot be essence, for in that case all things called one would have the same essence. Nor is it accident, for that which defines and separates the existing thing is truly called substance rather than accident; and this is what unity does. Accord- ingly Crescas defines unity as something essential to everything ac- tually existing, denoting the absence of plurality. This being true, that existent which is before all others is most truly called one. Also that being which is most separated from other things is best called one. Crescas disagrees with Maimonides's opinion that no positive at- tributes can be applied to God, such as indicate relation to his crea- tures, and so on. His arguments are that we cannot avoid relation to creatures even in the term "cause," which Maimonides admits; and in the attributes of action — the only kind of positive attributes al- lowed by Maimonides — it is implied that before a given time God did not do a particular thing, which he did later, a condition in God which Maimonides will not admit. Besides, if there are no positive attri-
