Iohannes Faber, a French jurist active in the first decades of the fourteenth century, expresses himself on the matter in the clearest of terms:
You can ask yourself why the incorporeal things are called iura or why they have a consistency of their own in the law. You must know that the legislators gave being to the law and called “beings” those iura which one can neither see nor touch physically. They nevertheless have a consistency and are considered notions of the mind or the result of an activity exercised by the mind. Therefore, when we read that the incorporeal things can neither be seen nor be touched, but are merely recognized by the mind and have consistency only in the sphere of thought, we understand why they are called iura. For good reason, because they have a substance given to them by the law, just as they are created and named by the law. (Faber 1546, 26va, ad Inst. 2.2)
Legal science,“is immediately subjected to theology.” The term “theology” is understood in its Aristotelian sense here, first science or metaphysics.
The Decretum [of Gratian, C. 16, q. 3, c. 17] states that the laws are divinely promulgated. But many ignorant people laugh at this and say: “Or you claim that the laws are made by God without mediation, which is not true for the civil laws; or you say that they are made by God through some mediating agency, which, however, could be said about any other things as well, and not only of the laws.” Those speaking similarly do not know what they are talking about, because discerning just from unjust is not given to man if not in obedience to divine indications. (Cynus 1578, 444vb, n. 2 ad Cod. 7.33.12)