e
same should apply to human laws.

Obj. 2: Further, by taking note of the past we can provide for the
future. Now unless human laws had been changed when it was found
possible to improve them, considerable inconvenience would have
ensued; because the laws of old were crude in many points. Therefore
it seems that laws should be changed, whenever anything better occurs
to be enacted.

Obj. 3: Further, human laws are enacted about single acts of man. But
we cannot acquire perfect knowledge in singular matters, except by
experience, which "requires time," as stated in _Ethic._ ii.
Therefore it seems that as time goes on it is possible for something
better to occur for legislation.

_On the contrary,_ It is stated in the Decretals (Dist. xii, 5): "It
is absurd, and a detestable shame, that we should suffer those
traditions to be changed which we have received from the fathers of
old."

_I answer that,_ As stated above (A. 1), human law is rightly
changed, in so far as such change is conducive to the common weal.
But, to a certain extent, the mere change of law is of itself
prejudicial to the common good: because custom avails much for the
observance of laws, seeing that what is done contrary to general
custom, even in slight matters, is looked upon as grave.
Consequently, when a law is changed, the binding power of the law is
diminished, in so far as custom is abolished. Wherefore human law
should never be changed, unless, in some way or other, the common
weal be compensated according to the extent of the harm done in this
respect. Such compensation may arise either from some very great and
every evident benefit conferred by the new enactment; or from the
extreme urgency of the case, due to the fact that either the existing
law is clearly unjust, or its observance extremely harmful. Wherefore
the Jurist says [*Pandect. Justin. lib. i, ff., tit. 4, De Constit.
Princip.] that "in establishing new laws, there should be evidence of
the benefit to be derived, before departing from a law which has long
been considered just."

Reply Obj. 1: Rules of art derive their force from reason alone: and
therefore whenever something better occurs, the rule followed
hitherto should be changed. But "laws derive very great force from
custom," as the Philosopher states (Polit. ii, 5): consequently they
should not be quickly changed.

Reply Obj. 2: This argument proves that laws ought to be changed: not
in view of any improvement, but