Metaphysics in the Middle Ages (continued) The observation of the radical contingency of things led the Persian philosopher Avicenna or Ibn Sinâ (980-1037), of the Shiite Muslim religion, to conceive of God as the Being who is necessarily (necesse esse). The things of this world are contingent, they do not necessarily exist. Their essence, what they are, does not imply their existence: the fact that they are, as proven by the fact that they appear and disappear. If they are, then they are because they have received the being of a being which is essentially and necessarily the uncaused cause of all contingent beings. This powerful thought played a decisive role in the history of medieval philosophy, as we shall see