Does the natural law contain many precepts or just one precept?

It seems that the natural law contains just one precept and not many precepts:

Objection 1:  As was explained above (q. 92, a. 2), law is contained under the genus precept.  Therefore, if the natural law contained many precepts, it would follow that there are likewise many natural laws.

Objection 2:  The natural law follows upon the nature of man.  But a human nature is one taken as a whole, even though it has multiple parts.  Therefore, either (a) there is just one precept of the law of nature because of the oneness of the whole or (b) there are many precepts because of the multiplicity of the parts of a human nature—in which case even what stems from the inclination of the concupiscible [part of the soul] will belong to the natural law.

Objection 3:  As was explained above (q. 90, a. 1), law is something that belongs to reason.  But there is just a single faculty of reason in a man.  Therefore, the natural law contains just one precept.

But contrary to this:  The precepts of the natural law play the same role in a man with respect to matters of action that first principles play with respect to matters of demonstration.  But there are many indemonstrable first principles.  Therefore, there are likewise many precepts of the natural law.

I respond:  As was explained above (a. 1), the precepts of the law of nature bear the same relation to practical reason that the first principles of demonstration bear to speculative reason.  For they are both principles that are known per se (per se nota).
Now there are two senses in which something is said to be known per se:  (a) in its own right (secundum se) and (b) as regards us (quoad nos).
Every proposition (propositio) said to be known per se in its own right is such that its predicate is part of the notion of its subject (de ratione subiecti); and yet it happens that such a proposition will not be known per se to someone who does not know the definition of the subject.  For instance, the proposition ‘A man is rational’ is known per se given its own nature, since anyone who expresses man expresses rational; and yet this proposition is not known per se to someone who does not know the real definition (quid sit) of man.  This is why, as Boethius points out in De Hebdomadibus, certain fundamental truths (dignitates) and propositions (propositiones) are known per se in general to everyone—and these are the ones whose terms are known to everyone, e.g., ‘Every whole is greater than its part’ and ‘Things equal to one and the same thing are equal to one another’—whereas other propositions are known per se only to the wise, who understand what the terms of the proposition signify.  For instance, to someone who understands that an angel is not a body it is known per se that an angel does not exist circumscriptively in a place; however, this is not obvious to unsophisticated people, who do not grasp the point in question.
Now there is a certain order among those things that fall within everyone’s apprehension.  The first thing to fall within apprehension is being, a grasp of which is included in everything that anyone apprehends.  So the first indemonstrable principle, founded upon the notions being and non‑being, is ‘One is not to affirm and deny [the same thing] at the same time’.  And, as Metaphysics 4 says, all the other principles are founded upon this one.
Now just as being is the first thing to fall within apprehension absolutely speaking, so good is the first thing to fall within the apprehension of practical reason, which is ordered toward action.  For every agent acts for the sake of an end, which has the character of a good.  And so the first principle in practical reasoning is what is founded on the notion good, which is the notion (supra rationem boni quae est):  “The good is what all things desire.”  Therefore, the first precept of law is that good ought to be done and pursued and that evil ought to be avoided.  And all the other precepts of the law of nature are founded upon this principle—so that, namely, all the things to be done or avoided that practical reason naturally apprehends as human goods are such that they belong to the precepts of the law of nature.  For since what is good has the character of an end and what is bad has the character of the contrary of an end, it follows that all the things man has a natural inclination toward are such that (a) reason naturally apprehends them as goods and thus as things that ought to be pursued by action and (b) reason naturally apprehends their contraries as evils and thus things that ought to be avoided.
Therefore, there is an ordering of the precepts of the natural law that corresponds to the ordering of the natural inclinations.
First, man has an inclination toward the good with respect to the nature he shares in common with all substances, viz., insofar as every substance strives for the conservation of its own esse in accord with its own nature.  And what belongs to the natural law in light of this inclination is everything through which man’s life is conserved or through which what is contrary to the preservation of his life is thwarted.
Second, man has an inclination toward certain more specific [goods] with respect to the nature that he shares in common with the other animals.  Accordingly, those things are said to belong to the natural law which nature teaches all the animals, i.e., the union of male and female, the education of offspring, etc.
Third, man has an inclination toward the good with respect to the rational nature that is proper to him, e.g., man has a natural inclination toward knowing the truth about God and toward living in society.  Accordingly, those things that are related to this sort of inclination belong to the natural law, e.g., that a man avoid ignorance, that he not offend the others with whom he has to live in community, and other such things related to this inclination.

Reply to objection 1:  Insofar as all these precepts of the law of nature are traced back to a single first principle, they have the character of a single natural law.

Reply to objection 2:  All the inclinations of any of the parts of human nature, e.g., the concupiscible part and the irascible part, are relevant to the natural law insofar as they are regulated by reason, and, as has been explained, they are traced back to a single first precept.  Accordingly, even though the precepts of the law of nature are many in themselves, they nonetheless share a single root.

Reply to objection 3:  Even if reason is in itself one, it nonetheless orders all the things relating to men.  Accordingly, the law of reason contains everything that can be regulated by reason.