The Precepts of Natural Law

There is a very good article in the January 2011 issue of The Thomist by Randall Smith, "What the Old Law Reveals about the Natural Law." I think St. Thomas's discussion of the moral precepts of the Old Law does illuminate his teachings about Natural Law and the first principles of practical reason. However, it is curious that Smith reduces the Natural Law to the two great commandments:

The natural law is grounded in two general, invariable precepts, which are invariable with respect to both rectitude and knowledge: to love God and to love neighbor as oneself. The natural law also contains a series of more specific precepts  derived from these first-level, general, invariable precepts (135).

Did he not remember I II 100, 5 ad 1?

Now there was need for man to receive a precept about loving God and his neighbor, because in this respect the natural law had become obscured on account of sin: but not about the duty of loving oneself, because in this respect the natural law retained its vigor: or again, because love of oneself is contained in the love of God and of one's neighbor: since true self-love consists in directing oneself to God. And for this reason the decalogue includes those precepts only which refer to our neighbor and to God.

According to Aquinas, there is a precept to love one's self, but it was not necessary for it to be promulgated as a separate commandment from God.

A reminder about St. Thomas on the fppr:

Now as "being" is the first thing that falls under the apprehension simply, so "good" is the first thing that falls under the apprehension of the practical reason, which is directed to action: since every agent acts for an end under the aspect of good. Consequently the first principle of practical reason is one founded on the notion of good, viz. that "good is that which all things seek after." Hence this is the first precept of law, that "good is to be done and pursued, and evil is to be avoided." All other precepts of the natural law are based upon this: so that whatever the practical reason naturally apprehends as man's good (or evil) belongs to the precepts of the natural law as something to be done or avoided. 

I think this post at Siris, On Grisez on the First Principle of Practical Reasoning, goes too far to make a distinction between the first principle of practical reason and the first principle of law, as it says the first principle of practical reason is "one founded," not that it is. 

(The Latin: "Et ideo primum principium in ratione practica est quod fundatur supra rationem boni, quae est, bonum est quod omnia appetunt. Hoc est ergo primum praeceptum legis, quod bonum est faciendum et prosequendum, et malum vitandum.")

Related:
SEP: Medieval Theories of Practical Reason
IEP: Medieval Theories of Practical Reason

Germain Grisez, "The First Principle of Practical Reason: A Commentary on the Summa Theologiae, 1-2, Question 94, Article 2"

Kelsen and Aquinas on “the Natural-Law Doctrine” by Robert P. George

An Overview of Practical Reason on Aquinas

THE LOGIC OF NATURAL LAW IN AQUINAS'S "TREATISE ON LAW" James Fieser