Is it correct to mark out moral
precepts of the Law in addition to the Decalogue?
It seems incorrect to mark out (distinguere)
moral precepts of the Law other than the Decalogue:
Objection 1: As our
Lord says in Matthew 22:40, “On these two precepts [of
charity] depends the whole Law and the prophets.”
But these two precepts are explicated by the ten precepts
of the Decalogue. Therefore, it is unnecessary
for there to be other moral precepts.
As has been explained (q. 99, a. 3), the moral precepts
are distinct from the judicial and ceremonial precepts.
But specifications of the general moral precepts are
contained in the judicial and ceremonial precepts,
whereas, as has been explained (a. 3), the general moral
precepts themselves are contained in the ten precepts of
the Decalogue—or are at least presupposed by the
Decalogue. Therefore, it is inappropriate for other moral
precepts to be handed down in addition to the Decalogue.
As was explained above (a. 2), the moral precepts are
about the acts of all the virtues. Therefore, just as, in
addition to the Decalogue, the Law has moral precepts that
deal with worship, generosity, mercy, and chastity, so too
there should be precepts dealing with the other virtues,
e.g., fortitude, sobriety, and others of this sort. But
such precepts are not to be found. Therefore, it is
incorrect to mark out in the Law other moral precepts that
go beyond the Decalogue.
But contrary to this:
Psalm 18:8 says, “The law of the Lord is pure, converting
souls.” But there are other moral precepts, in addition
to the Decalogue, through which a man is preserved without
the stain of sin and through which his soul is converted.
Therefore, the Law had other moral precepts to hand down
As is clear from what was said above (q. 99, a. 3‑4),
the judicial and ceremonial precepts have force solely
by virtue of their being instituted, since before they
were instituted, there was no apparent difference between
things being done one way or another. By contrast,
the moral precepts would have had efficacy on the basis
of the dictates of natural reason even if they had never
been codified in the Law.
Now there are three levels (gradus) of moral
(a) Some moral precepts are absolutely certain and so
evident that they do not need to be made known publically
(editione non indigent)—e.g., as was explained
above (a. 3), the commandments about love of God and
neighbor and others of this sort, which are, as it were,
the ends of the precepts (fines praeceptorum)
and so such that no one can make a mistaken judgment
of reason about them.
(b) Other moral precepts are more specific (determinata)
and such that anyone, even an ordinary man, can grasp
the reason behind them (ratio) easily and immediately.
However, since human judgment about these precepts can
be perverted in a few men, precepts of this sort need
to be made known publically (indigent editione).
These precepts are the precepts of the Decalogue.
(c) Still other moral precepts are such that the reason
behind them is not so evident to everyone; instead,
it is evident only to the wise. These precepts
are the ones that were added to the Decalogue and given
to the people by God through the mediation of Moses
Now since what is evident is the principle of cognition
for what is not evident, these other moral precepts
that were added to the Decalogue are traced back to
the precepts of the Decalogue in the sense that they
are a sort of addition to them.
For instance, the first precept of the Decalogue prohibits
the worship of strange gods, and to this are added other
precepts that prohibit things that are ordered toward
the worship of idols—as, e.g., in Deuteronomy 18:10‑11:
“Do not let there be found among you anyone that shall
purify his son or daughter by making them to pass through
the fire ..... . Neither let there be any evil
magician or enchanter, or anyone who consults prophetic
spirits, or fortune‑tellers, or who seeks truth
from the dead.”
The second precept of the Decalogue prohibits perjury,
and to this are added the prohibition of blasphemy in
Leviticus 24:15 and the prohibition of false teaching
in Deuteronomy 13.
To the third precept are added all the ceremonial precepts.
To the fourth precept, the one about honoring one’s
parents, is added a precept about honoring the elderly—this
according to Leviticus 19:32 (“Stand up in the presence
of a hoary head, and honor the elderly person”)—and,
more generally, all the precepts that induce one to
show respect for one’s betters or give benefits to one’s
equals or inferiors.
To the fifth precept, which prohibits homicide, are
added the prohibition of hatred or any sort of injury
(violatio) against one’s neighbor, as in Leviticus
19:16 (“You shall not stand against the blood of your
neighbor”), and the prohibition of hatred of one’s brother,
as in Leviticus 19:17 (“You shall not hate your brother
in your heart”).
To the sixth precept, which prohibits adultery, are
added the prohibition against prostitution (meretricium)—this
according to Deuteronomy 23:17 (“There shall be no prostitutes
among the daughters of Israel, nor fornicators among
the sons of Israel”)—and, again, the prohibition of
the vice against nature—this according to Leviticus
28:22-23 (“You shall not have sex with a male .....
You shall not copulate with any beast”).
To the seventh precept, which prohibits theft (furtum),
are added the precept prohibiting usury (usura)—this
according to Deuteronomy 23:19 (“You shalt not lend
your brother money to usury”)—and the prohibition of
fraud (fraus)—this according to Deuteronomy 25:13
(“You shall not have diverse weights in your bag”)—and,
more generally, everything having to do with the prohibition
of cheating (calumnia) and plundering (rapina).
To the eighth precept, which prohibits false witness,
are added the prohibition of false judgment—this according
to Exodus 23:2 (“You shall not acquiesce in judgment
to the opinion of the majority, so as to stray from
the truth”)—and the prohibition against lying, which
is added in the same place (“You shall avoid lying”),
and the prohibition against detraction—this according
to Leviticus 19:16 (“You shall not be a detractor (criminator)
or a whisperer among the people”).
no other precepts are added to the last two precepts
of the Decalogue, since these precepts prohibit all
evil desires in general.
Reply to objection 1:
The precepts of the Decalogue are ordered toward love of
God and neighbor with the evident rationale of what is
owed to them (secundum manifestam rationem debiti).
However, the additional precepts are ordered toward love
of God and neighbor with a more hidden rationale.
Reply to objection 2:
The ceremonial and judicial precepts specify the precepts
of the Decalogue by instituting something and not, as with
the additional moral precepts, by the force of natural
Reply to objection 3:
As was explained above (q. 90, a. 2), the precepts of
law are ordered toward the common good. And it
is because the virtues that order us to others are directly
relevant to the common good—and, likewise, chastity,
insofar as the act of generation subserves the common
good—that both the precepts of the Decalogue and the
additional precepts are given directly about these virtues.
By contrast, as far as the act of fortitude is concerned,
the relevant precept has to be proposed by leaders giving
exhortations in a war undertaken for the common good—as
is clear from Deuteronomy 20:3, where the priest is
commanded [to say], “Do not be afraid! Do not
Similarly, the prohibition
against gluttony is entrusted to paternal warnings,
since gluttony is contrary to the good of the household
(bonum domesticum). Hence, Deuteronomy
21:20 says in the personage of the parents, “He hates
listening to our admonitions; he is idle with his reveling
and debauchery and socializing.”