between the knowledge of one and the knowledge of the other. For whoever knows the root necessarily knows the branch, and whoever knows the branch necessarily knows the root. So, the knowledge of one is the knowledge of both. The explanation of this is that the root is the discourse that includes the prohibition of the self or necessitates the obligation of worship. So, whoever knows the discourse necessarily knows its implication. Its implication is compliance or avoidance. An example of this is the Almighty's saying: "Forbidden to you are the dead, blood, and the flesh of swine" (Al-Ma'idah / 3). The root is the prohibition, and the branch is the prohibition of consumption. And whoever knows the prohibition necessarily knows its implication.

It might be argued in objection to this cognitive necessity that many people know the verses of rulings that include commands and prohibitions. Yet, they are unable to determine the rulings derived from them, or they determine them incorrectly. This is evident in the differences among people in determining the ruling related to a single root. The answer is that what is meant by knowledge is correct knowledge that is based on the conditions of understanding, such as knowledge of the language and the styles of the Arabs in speech, and knowledge of the rules of discourse, its rulings, and its implications. If this correct knowledge of the root is complete, then the knowledge of the ruling it necessitates is necessarily complete.

This ruling, which Al-Mahdi established regarding the relationship between knowing the root and knowing the branch, is based on a ruling of inherent necessity. This is the obligation of knowing the necessitated by knowing the necessitant, and vice versa. If you see the sun's rays (a necessitated thing), you will necessarily know the existence of the sun (a necessitant) on the horizon, even if you do not see it directly. Likewise, if you know the existence of the sun on the horizon, you will necessarily know the diffusion of its rays on the earth. Al-Mahdi clarified that the necessity between knowing the root and knowing the branch is an intellectual necessity, as he says: "As for the connection of knowing the branch to knowing the root, and the connection of knowing the root to knowing the branch, and the necessity between them in knowing both by knowing one of them, it is an intellectual connection and a strong necessity."

(Same source: 143) Ibn Tumart: The most precious thing (144) is sought.