Reason and its limits. The realm of creed and the realm of Sharia: First: The role of reason in the realm of creed: Reason is the primary means of perceiving the truths of creed. Man needs to know that God exists, that He is One, that He is transcendent, and that there is reward and punishment. Sensation is certainly not a path to this, nor is hearing, because these matters are not valid for knowledge by hearsay. Therefore, reason is the only means of knowing them. "By the necessity of reason, the existence of the Creator is known," and "By the necessity of reason, His oneness is known."

Reason can not only examine and grasp these truths when the religious text presents them, but it can also grasp them independently and from the outset. This is what we can infer from linking the perception of these truths with the necessity of reason. Since the necessity of reason exists with or without the advent of Sharia, does this mean that man is obligated to believe in creed by virtue of reason, whether Sharia has reached him or not? We do not find a clear statement from Al-Mahdi to this effect. However, it is likely that this is his doctrine, as his grounding of the perception of creed in the necessity of reason suggests. Thus, he would be closer to the Mu'tazilite doctrine on this issue.

However, although reason is the means of perceiving creed, it has a limit in this perception. That limit is the aspect of certainty in the truths. As for the aspect of "how" (kayf), it is beyond its capacity. To go beyond this limit and delve into the realm of "how" is to fall into the pitfall of anthropomorphism. Al-Mahdi said: "The intellect has a limit at which it stops and does not exceed. It is the inability to describe 'how' (takyeef). It has no realm beyond that, and seeking it leads to embodiment and negation." Based on this fact, Ibn Tumart warned: "The most precious thing to seek: Creed." "Theology: Creed." "A treatise on the fact that Tawhid is the basis of religion."

See the details of the Mu'tazilite views on this in: Al-Qadi Abd al-Jabbar, Sharh al-Usul al-Khamsa, and onwards. "Creed: Ibn Tumart."