of the Imāmiyyah (1) are established by them through consensus, since their principal grounds for the foundations of their religion are the rational arguments they present, consensus, and the reports they transmit. They say (2): “This is known through reason, because people must have (3) an infallible imam and an imam explicitly designated by a text; and no one other than Ali is infallible or explicitly designated by a text * according to consensus. Therefore, Ali must be the infallible one”—along with other such premises in their arguments.
They are then told * (4): If consensus is not authoritative proof, those arguments are invalid, as are the doctrinal foundations they have built upon consensus. Their position is therefore invalid; and if it is invalid, the position of Ahl al-Sunnah is established.
If consensus is valid, the position of Ahl al-Sunnah is likewise established. Thus, the invalidity of their position is clear whether or not they affirm that consensus is authoritative proof. Once their position is invalidated, the position of Ahl al-Sunnah is established (5), which is what was to be demonstrated.
If they say: “We set consensus aside and do not invoke it as proof for any of our doctrinal foundations. We rely only on reason and reports transmitted from the infallible imams,”
they are told: If you do not invoke consensus as proof, you have no transmitted proof remaining except reports known to come from the Prophet—may Allah bless him and grant him peace. For what they transmit from Ali and the other imams cannot constitute proof until we know that the particular imam concerned is infallible.