As stated above (90, A1,2),
law is framed as a rule or measure of
human acts. Now a measure should be homogeneous with that which it measures, as stated in Metaph. x, text. 3,4, since different things are measured by different measures. Wherefore laws imposed on men should also be in keeping with their condition, for, as Isidore says (Etym. v, 21),
law should be “possible both according to
nature, and according to the customs of the country.” Now possibility or faculty of action is due to an interior
habit or disposition: since the same thing is not possible to one who has not a
virtuous habit, as is possible to one who has. Thus the same is not possible to a child as to a full-grown
man: for which reason the
law for children is not the same as for adults, since many things are permitted to children, which in an adult are punished by
law or at any rate are open to blame. In like manner many things are permissible to men not perfect in
virtue, which would be intolerable in a
virtuous man.
Now
human law is framed for a number of
human beings, the majority of whom are not perfect in
virtue. Wherefore
human laws do not forbid all vices, from which the
virtuous abstain, but only the more grievous vices, from which it is possible for the majority to abstain; and chiefly those that are to the hurt of others, without the prohibition of which
human society could not be maintained: thus
human law prohibits murder, theft and such like.
**. . . . **
Reply to Objection 2. The purpose of
human law is to lead men to
virtue, not suddenly, but gradually. Wherefore it does not lay upon the multitude of imperfect men the burdens of those who are already
virtuous, viz. that they should abstain from all
evil. Otherwise these imperfect ones, being unable to bear such precepts, would break out into yet greater evils: thus it is written (
Psalm 30:33): “He that violently bloweth his nose, bringeth out blood”; and (
Matthew 9:17) that if “new wine,” i.e. precepts of a perfect life, “is put into old bottles,” i.e. into imperfect men, “the bottles break, and the wine runneth out,” i.e. the precepts are despised, and those men, from contempt, break into evils worse still.