One of the issues which Muslim theologians over the centuries have debated – and that is the breadth of knowledge which the Prophets, Messengers, Imams and Saints (al-Awliyaʾ) possess. Where does it come from, and how and when are they permitted to make use of it? The term that has been coined for this special knowledge is ‘ilm al-ghayb – which literally means ‘knowledge of the unseen.’ This article seeks to better understand the roots of this discussion; review who amongst the creations of Allah have been privileged with knowledge of the unseen; how are they are endowed with it; and how does it compare to the knowledge of Allah?