This paper deals with the contingence or necessity of the causal relationship between the Prime Cause and its effect, as treated by Avicena and Thomas Aquinas. In order to this, we consider the parallel treatments of Divine Intelligence and Will in both authors. They agree that God knows Himself and by doing so, He also knows the things other than Him. Likewise, that He loves or wants Himself and by doing so, He accidentally wants the things other than Him. However, their conclusion regarding the contingence or necessity of the world is not the same. According to Avicena, the world is possible in itself but necessary with relation to another. According to Aquinas, that God wants the world with hypothetical necessity refers to the necessity of His will, without determining the contingence or necessity of the world in itself. In fact, a universe in which necessity and contingence are combined is preferable, in Aquinas’s view, because it represents in a better way God’s multiple perfections.