Scholars offered different accounts of the nature of reason: a faculty of the soul, a substance in some philosophical vocabularies, or a non-bodily reality connected with understanding and direction of action.
وَقِيلَ: جَوْهَرٌ
And it has also been said: a substance.
These terms should not be treated as interchangeable. Identifying the function of reason does not settle every metaphysical dispute about what kind of entity it is. The reliability of a sound inference is a further question, distinct from these competing descriptions of the faculty itself.