[Excerpted from An Austrian Perspective on the History of Economic Thought.]
In a profound sense … 18th-century natural-rights theory was a refined variant of medieval and post-medieval Scholastic natural law. The rights were now clearly individualistic and not societal or pertaining to the state; and the set of natural laws was discoverable by human reason.
The 17th-century Dutch Protestant, and in essence Protestant Scholastic, Hugo Grotius, deeply influenced by the late Spanish Scholastics, developed a natural-law theory which he boldly declared was truly independent of the question of whether God had created them. The seeds of this thought were in St Thomas Aquinas and in later Catholic Scholastics, but never had it been formulated as clearly and as starkly as by Grotius. Or, to put it in terms that had fascinated political philosophers since Plato: did God love the good because it was in fact good, or is something good because God loves it? The former has always been the answer of those who believe in objective truth and objective ethics, that is, that something might be good or bad in accordance with the objective laws of nature and reality. The latter has been the answer of fideists who believe that no objective rights or ethics exist, and that only the purely arbitrary will of God, as expressed in revelation, can make things good or bad for mankind. Grotius’s was the definitive statement of the objectivist, rationalist position, since natural laws for him are discoverable by human reason, and the 18th-century Enlightenment was essentially the spinning out of the Grotian framework.
To Grotius the Enlightenment added Newton, and his vision of the world as a set of harmonious, precisely if not mechanically interacting natural laws. And while Grotius and Newton were fervent Christians as was almost everyone in their epoch, the 18th century, starting with their premises, easily fell into deism, in which God, the great "clock-maker," or creator of this universe of natural laws, then disappeared from the scene and allowed his creation to work itself out.
From the standpoint of political philosophy, however, it mattered little whether Quesnay and the others (Du Pont was of Huguenot background) were Catholics or deists: for given their world outlook, their attitude toward natural law and natural rights could be the same in either case.