Although his modern readers have little inclination to discriminate among the three foci (natural law in the mind, in nature, in the mind of God) or to reflect upon their order of priority, Thomas understood what is at stake in arriving at a proper definition. The fact that we first perceive ourselves discovering or grasping a rule of action does not mean that human mind is first in the causal order, or in the ultimate order of being.

For example, the judge who discovers a rule does not equate the cause of discovery with the cause of the rule—unless, perchance, they are one and the same. In the case of natural law, Thomas defines the law from the standpoint of its causal origin (that is, what makes it a law), not in terms of a secondary order of causality through which it is discovered (the human intellect).

Without the order of priority, we have either nature or the hu man mind as the cause or the law —not the cause of knowing or discovering, but the cause of the law itself. This would destroy the metaphysical continuity between the various dispensations of divine providence. For if God is to govern, he will have to supersede, if not destroy, the jurisdiction constituted (allegedly) by human causality. Insofar as the natural law is regarded as the foundation of the moral order, and insofar as that is thought to be caused (and not merely discovered) in some proper and primary way by human cognition, God will have t o unseat the natural law. Almost all the modern theories of natural law seek to relieve that conflict in favor of what is first in the human mind. Thomas understood what is at stake in giving definitions, and was exceedingly careful not to confuse what is first in human cognition with what is first in being.

Natural Law and Catholic Moral Theology, p. 6 parr. 2 y 3