المعنى الاصطلاحي :

The cognitive instinct by which Allah has distinguished man from other living beings. Losing reason renders the person no longer competent for religious assignments.

الشرح المختصر :

"‘Aql" (reason/intellect) refers to the ability and readiness to accept knowledge and understand speech, and to distinguish between what is good and what is bad, and between truth and falsehood. It is a description of the fundamental functions of the brain, such as thinking, understanding, and the like. It is also called "nuha", "lubb", "hijr", and otherwise. "‘Aql" differs from one person to another. "‘Aql" is a condition for being competent for religious assignment and a means for acquiring knowledge and experience. By reason, the religion and deeds are perfected. "‘Aql" is of two categories: 1. Natural instinctual "‘aql", which is the means for acquiring knowledge. 2. Gained and acquired "‘aql", which is the effect and outcome of learning knowledge. If these two are joined together in a person, he attains perfection and his affairs are set right. "Instinctual" means that Allah initially created the person that way, and it was not something acquired by him.

التعريف اللغوي المختصر :

"‘Aql": perception, knowledge. Opposite: "humq" (foolishness) "jahl" (ignorance). Original meaning: prevention and detention. Other meanings: understanding and discretion.