They asked us and said: The son of al-Hasan has not appeared openly to both the elite and the general public—so how do you know he exists in the world? Have you seen him, or has a group with widely transmitted reports told you they saw and witnessed him?

We reply: All matters of religion are known through reasoning. We came to know Allah, the Mighty and Majestic, through evidence—though we did not see Him, nor did anyone who saw Him inform us. We knew of the Prophet ﷺ and his presence in the world through reports, and we confirmed his prophethood and truthfulness through reasoning. We knew that he appointed Ali b. Abi Talib through reasoning as well. We also knew that the Prophet ﷺ and all the Imams after him were knowledgeable of the Book and the Sunnah, and that it is impossible for them to err, forget, or intentionally lie in such matters. Likewise, through reasoning we came to know that al-Hasan b. Ali was an Imam whose obedience was obligatory. And we knew from mass-transmitted reports of the truthful Imams that the Imamate, after being in al-Hasan and al-Husayn , could only be in the children of the Imam—not in a brother or other relative. Thus, the Imam could not pass without having appointed one of his sons as Imam. Once the Imamate of al-Hasan and the truth of his death were established, it followed that he had appointed one of his sons as Imam. This is one line of reasoning for his existence.

Another proof is that al-Hasan left behind a group of trustworthy men who narrated from him what is lawful and unlawful, handled the books and wealth of his Shia, and issued written responses. These men held a position of discretion and integrity, having been appointed by him in his lifetime. After his passing, they unanimously agreed that he had left behind a son who was the Imam. They instructed the people not to ask about his name and to conceal his identity from his enemies. The ruling authority pursued him with intensity, even assigning guards to the houses and pregnant women among al-Hasan’s concubines. After that, letters continued to arrive from his son to the Shia, containing commands and prohibitions, sent through his father's trusted men, for over twenty years.

Then the correspondence ceased. Most of al-Hasan’s companions who had testified about the Imam after him passed away, and only one man remained, whose reliability and trustworthiness were unanimously affirmed. He ordered the people to maintain secrecy and not to disclose anything about the Imam. The correspondence then ended. Thus, the existence of the Imam was confirmed for us through the reasoning mentioned above, through what was reported by the companions and agents of al-Hasan , and through the authenticity of the narrations about his occultation—narrations which are well-known—and that he would have two occultations, one more severe than the other.