...loving God above all else is an act that conforms to natural right reason, which dictates that what is best should be loved the most, and consequently the act is right in and of itself. Indeed, its rightness is self-evident, as the rightness of a first principle in the domain of possible actions. For something should be loved the most, and that is nothing other than the highest Good, just as nothing other than the highest Truth should be most firmly held as true by the intellect. And this argument is confirmed by the consideration that moral precepts belong to the natural law; consequently, "You shall love the Lord your God," etc. belongs to the natural law, and thus the fact that this act is right is known [naturally].
From this it follows that there can be a virtue that naturally inclines to that act--and it is a theological virtue, since it has to do with the theological object: that is, it has to do immediately with God. And not only that, but it also depends immediately on the first rule of human acts and has to be infused by God; for this virtue is apt to perfect the highest part of the soul, which receives its full and complete perfection in only one way: immediately from God.
[John Duns Scotus, Selected Writings on Ethics, Thomas Williams, ed. and tr. Oxford UP (New York: 2017) pp. 162-163.]