as Allah Almighty has said: ﴿وَرَفَعْنَا بَعْضَهُمْ فَوْقَ بَعْضٍ دَرَجَاتٍ لِيَتَّخِذَ بَعْضُهُمْ بَعْضًا سُخْرِيًّا﴾[1]; “And We raised some of them above others in rank so that some of them would take others in service.”

Of course, the perceptions of the intellect are not simple; rather, their levels differ in each person according to the amount of knowledge and its impediments within him; and they include illusion, meaning a defeated probability, doubt, meaning an equal probability, conjecture, meaning a dominant probability, and certainty, meaning the absence of any probability of contradiction. Nevertheless, although they all arise from the intellect, what is considered the criterion for knowing is only certainty; because illusion, doubt, and conjecture conflict to a greater or lesser degree with their opposite probabilities. Thus, they themselves require a criterion for knowing to determine the correctness of one of the two probabilities within them. That criterion is certainty, which has no opposite probability; therefore, its authority is intrinsic and self-evident. From here, it is understood that the foundation of human understanding is only certainty, and any understanding that does not lead to certainty has no validity; as Allah Almighty has said: ﴿إِنَّ الظَّنَّ لَا يُغْنِي مِنَ الْحَقِّ شَيْئًا﴾[2]; “Indeed, conjecture is not sufficient for (proving) the truth,” whereas conjecture is the strongest perception of the human being after certainty, and his other perceptions are weaker than it by degrees; consequently, they are not considered as proof by even greater reason.

Self-Evidence of the Intellect

The intellect is the primary source of understanding and the first criterion for knowledge, and its authority is certainly self-evident; because it is impossible to conceive of it except by affirming it, and affirming it is inseparable from conceiving of it. Rather, it can be said that authority itself is an intellectual matter, and it has no meaning other than revealing the reality to the intellect. Therefore, proving the authority of the intellect is like proving the authority of authority! In other words, the authority of anything used as evidence to prove the authority of the intellect is not clearer than the authority of the intellect itself, and proving it is conditional on the establishment of the authority of the intellect.