seek to demonstrate God's existence through his creations. The proof then became known in the Arabic tradition as the "Proof of the Truthful" (burhan al-siddiqin). Argument The necessary existent Avicenna distinguishes between a thing that needs an external cause in order to exista contingent thingand a thing that is guaranteed to exist by its essence or intrinsic naturea necessary existent. The argument tries to prove that there is indeed a necessary existent. It does this by first considering whether the opposite could be true: that everything that exists is contingent. Each contingent thing will need something other than itself to bring it into existence, which will in turn need another cause to bring it into existence, and so on. Because this seemed to lead to an infinite regress, cosmological arguments before Avicenna concluded that some necessary cause (such as God) is needed to end the infinite chain. However, Avicenna's argument does not preclude the possibility of an infinite regress. Instead, the argument considers the entire collection (jumla) of contingent things, the sum total of every contingent thing that exists, has existed, or will exist. Avicenna argues that this aggregate, too, must obey the rule that applies to a single contingent thing; in other words, it must have something outside itself that causes it to exist. This cause has to be either contingent or necessary. It cannot be contingent, though, because if it were, it would already be included within the aggregate. Thus the only remaining possibility is that an external cause is necessary, and that cause must be a necessary existent. Avicenna anticipates that one could reject the argument by saying that the collection of contingent things may not be contingent. A whole does not automatically share the features of its parts; for example, in mathematics a set of numbers is not a number. Therefore, the objection goes, the step in the argument that assumes that the collection of contingent things is also contingent, is wrong. However, Avicenna dismisses this counter-argument as a capitulation, and not an objection at all. If the entire collection of contingent things is not contingent, then it must be necessary. This also leads to the conclusion that there is a necessary existent, the very thing Avicenna is trying to prove. Avicenna remarks, "in a certain way, this is the very thing that is sought". From the necessary existent to God The limitation of the argument