 Avicenna next considers the aggregate of all the existing contingent individual things, the existence of each of which is accounted for by its causal antecedents. He then proposes and evaluates four options for accounting for the aggregate’s existence. The first is that the existence of the aggregate does not require a cause. However, given the principle that the existence of any contingent thing must have a cause, the aggregate would then have to exist necessarily. But the aggregate’s existing necessarily is ruled out by the fact that all of the individuals in it are contingent things. On the second option, the cause of the existence of the aggregate is “the individuals all together.” But then the aggregate would cause itself to exist, which is ruled out by the principle that the existence of any contingent thing requires a cause other than it. The third option is that the cause of the aggregate is one of the individuals in it. But all of those individuals are caused to exist by other things in the aggregate, so no one individual is qualified to be the cause of the existence of the entire aggregate. The only remaining option is that the existence of the aggregate has a cause external to the aggregate. Because all of the contingently existing things are in the aggregate, the cause must be a necessarily existing thing (Mayer 2001). Avicenna is fully aware that the argument shouldn’t end here, since it must be shown that the necessarily existing thing is God, and he provides a number of considerations in favor of this claim (Adamson 2013).