The word intellect is the preferred translation of the Arabic word ‘aql, in keeping with the original meaning of intellectus in Latin Christendom, or nous in the Greek. Reason, on the other hand, better translates as ratio in the Latin and the Greek dianoia.
For whereas the intellect/nous is capable of a direct contemplative vision of transcendent realities, Reason is of an indirect, discursive nature; it works with logic and arrives at mental concepts, only within those realities.
With the intellect, then, one can effectively contemplate or ‘see’ the Real. With reason, one can think about it. Losing sight of this distinction entails the reductive view of knowledge that has increasingly characterised western epistemology since the end of the Middle Ages.
(c.f. Knowledge and the Sacred, S.H. Nasr, 1981; Principles of Epistemology in Islamic Philosophy, Mehdi Yazdi, 1992; From Religion to Philosophy, F.M. Concord, 1957)
Cross-reference with this quote:
The heart has reasons that reason cannot know. – Pascal Blaise