; in another way, as in that which is
ruled and measured, since a thing is ruled and measured, in so far as
it partakes of the rule or measure. Wherefore, since all things
subject to Divine providence are ruled and measured by the eternal
law, as was stated above (A. 1); it is evident that all things
partake somewhat of the eternal law, in so far as, namely, from its
being imprinted on them, they derive their respective inclinations to
their proper acts and ends. Now among all others, the rational
creature is subject to Divine providence in the most excellent way,
in so far as it partakes of a share of providence, by being provident
both for itself and for others. Wherefore it has a share of the
Eternal Reason, whereby it has a natural inclination to its proper
act and end: and this participation of the eternal law in the
rational creature is called the natural law. Hence the Psalmist after
saying (Ps. 4:6): "Offer up the sacrifice of justice," as though
someone asked what the works of justice are, adds: "Many say, Who
showeth us good things?" in answer to which question he says: "The
light of Thy countenance, O Lord, is signed upon us": thus implying
that the light of natural reason, whereby we discern what is good and
what is evil, which is the function of the natural law, is nothing
else than an imprint on us of the Divine light. It is therefore
evident that the natural law is nothing else than the rational
creature's participation of the eternal law.

Reply Obj. 1: This argument would hold, if the natural law were
something different from the eternal law: whereas it is nothing but a
participation thereof, as stated above.

Reply Obj. 2: Every act of reason and will in us is based on that
which is according to nature, as stated above (Q. 10, A. 1): for
every act of reasoning is based on principles that are known
naturally, and every act of appetite in respect of the means is
derived from the natural appetite in respect of the last end.
Accordingly the first direction of our acts to their end must needs
be in virtue of the natural law.

Reply Obj. 3: Even irrational animals partake in their own way of the
Eternal Reason, just as the rational creature does. But because the
rational creature partakes thereof in an intellectual and rational
manner, therefore the participation of the eternal law in the
rational creature is properly called a law, since a law is something
pertaining to reason, as stated above (Q. 90, A.