The proof of the second principle being the feature of the Imam; that his infallibility must be ascertained, is that we need the Imam due to our fallibility, for if the people were infallible, they would never need an Imam. They need him since they are fallible. This leads us to conclude that the reason for the need of an Imam is people’s fallibility. Like we say about the reason for need of an effect to its cause is its occurrence (huduth), due to the fact that an entity having huduth needs a cause, and an entity that does not have huduth, never needs a cause. So we conclude that every effect needs a cause. Similarly, the need of every fallible to an Imam must be acknowledged, or the rule of causality will be violated. Now, if the Imam is himself fallible, he would also be needful of an infallible Imam. The same argument applies to his Imam, leading to the conclusion of an infinite number of Imams or to an infallible Imam, which is our purpose. We have established this argument in our books, therefore, we will not prolong the inquiry by raising further questions and answering them, as the purpose of this book is different from other books and this much suffices.