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