e then law would cease, when
the act of reason ceases, for instance, while we are asleep.
Therefore law is nothing pertaining to reason.

Obj. 3: Further, the law moves those who are subject to it to act
aright. But it belongs properly to the will to move to act, as is
evident from what has been said above (Q. 9, A. 1). Therefore law
pertains, not to the reason, but to the will; according to the words
of the Jurist (Lib. i, ff., De Const. Prin. leg. i): "Whatsoever
pleaseth the sovereign, has force of law."

_On the contrary,_ It belongs to the law to command and to forbid.
But it belongs to reason to command, as stated above (Q. 17, A. 1).
Therefore law is something pertaining to reason.

_I answer that,_ Law is a rule and measure of acts, whereby man is
induced to act or is restrained from acting: for _lex_ (law) is
derived from _ligare_ (to bind), because it binds one to act. Now the
rule and measure of human acts is the reason, which is the first
principle of human acts, as is evident from what has been stated
above (Q. 1, A. 1, ad 3); since it belongs to the reason to direct to
the end, which is the first principle in all matters of action,
according to the Philosopher (Phys. ii). Now that which is the
principle in any genus, is the rule and measure of that genus: for
instance, unity in the genus of numbers, and the first movement in
the genus of movements. Consequently it follows that law is something
pertaining to reason.

Reply Obj. 1: Since law is a kind of rule and measure, it may be in
something in two ways. First, as in that which measures and rules:
and since this is proper to reason, it follows that, in this way, law
is in the reason alone. Secondly, as in that which is measured and
ruled. In this way, law is in all those things that are inclined to
something by reason of some law: so that any inclination arising from
a law, may be called a law, not essentially but by participation as
it were. And thus the inclination of the members to concupiscence is
called "the law of the members."

Reply Obj. 2: Just as, in external action, we may consider the work
and the work done, for instance the work of building and the house
built; so in the acts of reason, we may consider the act itself of
reason, i.e. to understand and to reason, and something produced by
this act. With regard to the speculative reason, this is first of all
the definition; secondly, the proposition; thirdly, the syllogism or
argument. An