One of his confidants warned him of the escalating situation, so he left the city with ten of his companions, heading towards Aghmat.

In this city, he resumed teaching and preaching. He found that some scholars opposed him with harshness and took a stance of sharp opposition. A famous debate took place between him and them concerning knowledge and its methods, and the principles of truth and falsehood. He asked his opponents to present a man from among themselves to debate him. He would then ask him questions, explain the error in his answer, and elaborate on the correct answer. It is mentioned that he asked his opponent: "Are the methods of knowledge limited or unlimited?" He replied: "Yes, they are limited to the Book and the Sunnah and the meanings they indicate." He told him: "I only asked if the methods of knowledge are limited or not. You only mentioned one of them, and the answer must correspond to the question. He did not understand him and was unable to answer. Then he asked him: "What are the principles of truth and falsehood?" He returned to his first answer. When he was unable to understand the question, let alone answer it, Ibn Tumart began to explain the principles of truth and falsehood, saying: "The principles of truth and falsehood are four: knowledge, ignorance, doubt, and conjecture. Knowledge is the basis of guidance, and ignorance, doubt, and conjecture are the basis of misguidance."

After a few days of staying in Aghmat, he left with his companions towards his hometown.

See: Ibn Abi Zar', Rawd al-Qirtas, p. 176.

Al-Baydaq mentioned that among them was Abd al-Haqq ibn Ibrahim, who "used to harm the Infallible and envy him for what God had given him of knowledge and understanding." However, a group of other sources mention this scholar as a friend of Ibn Tumart who sought to help him.

See: Al-Istiqsa', vol. 50, p. 5; Al-Sallawi, vol. 50, p. 5. See also: Ibn Khallikan, Wafiyat al-A'yan, vol. 2, p. 121.

Rawd al-Qirtas, p. 122, states that this debate took place in Aghmat and did not occur in the presence of the Amir, as mentioned by Ibn Abi Zar'. It is also understood from the words of Al-Baydaq that the Infallible departed from Aghmat after silencing them with his knowledge and refuting them with clear arguments for the general and specific. He did not transmit the text of the debate because of the subtle meanings it contained.

He appears to have had little knowledge in his writings.

See the full debate in: Ibn Tumart, A'azz ma Yutlab, p. 140; Sharh A'azz ma Yutlab, p. 48; Rawd al-Qirtas, pp. 121-122.