Kitāb al-Ghayba > Philosophy and wisdom of Occultation
Hadith #1

فإذا ثبت بطلان هذه الأقاويل كلها لم يبق إلا القول بإمامة ابن الحسن عليه السلام، وإلا لأدى إلى خروج الحق عن الأمة وذلك باطل. وإذا ثبتت إمامته بهذه السياقة ثم وجدناه غائبا عن الأبصار علمنا أنه لم يغب مع عصمته وتعين فرض الإمامة فيه وعليه إلا لسبب سوغه ذلك وضرورة ألجأته إليه وإن لم يعلم على وجه التفصيل.

Having established the invalidity of all these beliefs, the only creed that remains is that of Imamate of Ibn Hasan (a.s) or else it would follow that truth is beyond this Ummah. When his Imamate is proved through this reasoning and we find him hidden from people, considering his infallibility and that the duties of Imamate fall on his person and on his shoulders, we infer that he has not disappeared, but for a reason that has allowed it and a necessity that has compelled him to it, even if we may not know it in detail. This is analogous to the diseases, which afflict children and cattle, and the creation of harmful elements, repulsive faces and ambiguous verses of Quran.