It is impossible to establish a ruling without it being based on a principle, and its basis requires the establishment of its foundation. The fact that conjecture is its foundation necessitates its inversion, as it is impossible to establish it except with knowledge. The fact that the basis of the ruling, which is the opposite of knowledge (i.e., presumed conjecture), is knowledge necessitates the negation of the basis of the ruling (the conjecture we presumed, as it inverts to knowledge) while the ruling exists. Describing knowledge with the opposite of its characteristic and the opposite of knowledge (i.e., conjecture) with the opposite of its characteristic necessitates the invalidity of what is transmitted and what is reasoned, and their invalidity is impossible.

In this argument, there is also a superficial aspect: it proceeds to argue that conjecture cannot be a source of ruling, based on the prior conviction that only knowledge can be a source of ruling. This implies that conjecture is not a principle. Thus, the premise includes the conclusion.

This rejection of conjecture as a principle for rulings was adopted by most of the scholars who adhered to texts and denounced opinion as a source of ruling. The Zahiris were at the forefront of these, as they considered opinion to be mere speculation. Therefore, basing a ruling on it is basing it on conjecture, and the Sharia is not based on conjecture, for conjecture avails nothing against the truth. Ibn Hazm was very critical of those who based their rulings on conjecture by using analogy, saying that this is an admission that they do not trust it at all, and this is ruling by conjecture, which is forbidden by the text of the Quran: "Conjecture avails nothing against the truth." (Surah Yunus, verse 36). And by the text of the Prophet's ruling, when he said: "Beware of conjecture, for conjecture is the most deceitful of speech." (Narrated by Bukhari in the Book of Wills, chapter: The saying of Allah Almighty: "after the execution of his will or his debt"). If the Quran and Sunnah are clear, then it is invalid, and the invalid cannot be a basis for the truth.