Imam Ali (a.s) asked Imam Hassan (a.s) and Imam Hussein (a.s) the difference between faith and certitude. They remained silent. Then he asked Imam Hassan (a.s) to answer him. Imam Hassan (a.s) said: “There is only one hand-breadth distance between the two.” Imam Ali (a.s) asked: “How come?” He replied: “Since faith is related to what we hear and acknowledge with our heart, and certitude is related to what we see and use to argue in favor of what we cannot see.