Third Set of Readings by St. Thomas Aquinas
First Part of the Second Part (Prima Secundæ Partis)
Question 90. The essence of law
Article 1. Whether law is something pertaining to reason?
It belongs to the law to command and to forbid. But it belongs to reason to command, as stated
above (Question 17, Article 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 (1, 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 to Objection 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. And since also the practical reason makes use of a syllogism
in respect of the work to be done, as stated above (13, 3; 76, 1) and since as the Philosopher
teaches (Ethic. vii, 3); hence we find in the practical reason something that holds the same
position in regard to operations, as, in the speculative intellect, the proposition holds in regard to
conclusions. Such like universal propositions of the practical intellect that are directed to actions
have the nature of law. And these propositions are sometimes under our actual consideration,
while sometimes they are retained in the reason by means of a habit.
Reply to Objection 3.
Reason has its power of moving from the will, as stated above (Question
17, Article 1): for it is due to the fact that one wills the end, that the reason issues its commands
as regards things ordained to the end. But in order that the volition of what is commanded may
have the nature of law, it needs to be in accord with some rule of reason. And in this sense is to
be understood the saying that the will of the sovereign has the force of law; otherwise the
sovereign's will would savor of lawlessness rather than of law.
Article 2. Whether the law is always something directed to the common good?