Reason is the faculty of knowing indirectly in the absence of a direct vision and with the help of points of reference. (GTUFS: LogicT, Evidence and Mystery)
Reason / Intellect: Reason is formal by its nature and formalistic in its operations; it proceeds by coagulations, by alternatives and by exclusions – or, it can be said, by partial truths. It is not, like pure intellect, formless and fluid light; true, it derives its implacability, or its validity in general, from the intellect, but it touches on essences only through drawing conclusions, not by direct vision; it is indispensable for verbal formulation but it does not involve immediate knowledge. (GTUFS: UIslam, Islam)
Reason is not Intelligence in itself, it is only its instrument, and this on the express condition that it be inspired by intellectual Intuition, or simply correct ideas or exact facts; nothing is worse than the mind cut off from its root; corruptio optimi pessima. The Intellect – aliquid increatum et increabile – dominates and ennobles our fundamental faculties: it is by it that our Reason exists and that it is objective and total; and again it is by it that our Will is free, hence capable of moral heroism, and that our Sentiment is disinterested, hence capable of compassion and generosity. (GTUFS: TransfMan, Faculties and Modalities of Man)