Wherefore theft and
robbery derive their sinful nature, through the taking being
involuntary on the part of the person from whom something is taken.
Now the involuntary is twofold, namely, through violence and through
ignorance, as stated in _Ethic._ iii, 1. Therefore the sinful aspect
of robbery differs from that of theft: and consequently they differ
specifically.

Reply Obj. 1: In the other kinds of sin the sinful nature is not
derived from something involuntary, as in the sins opposed to
justice: and so where there is a different kind of involuntary, there
is a different species of sin.

Reply Obj. 2: The remote end of robbery and theft is the same. But
this is not enough for identity of species, because there is a
difference of proximate ends, since the robber wishes to take a thing
by his own power, but the thief, by cunning.

Reply Obj. 3: The robbery of a woman cannot be secret on the part of
the woman who is taken: wherefore even if it be secret as regards the
others from whom she is taken, the nature of robbery remains on the
part of the woman to whom violence is done.
_______________________

FIFTH ARTICLE [II-II, Q. 66, Art. 5]

Whether Theft Is Always a Sin?

Objection 1: It would seem that theft is not always a sin. For no sin
is commanded by God, since it is written (Ecclus. 15:21): "He hath
commanded no man to do wickedly." Yet we find that God commanded
theft, for it is written (Ex. 12:35, 36): "And the children of Israel
did as the Lord had commanded Moses [Vulg.: 'as Moses had
commanded']. . . and they stripped the Egyptians." Therefore theft is
not always a sin.

Obj. 2: Further, if a man finds a thing that is not his and takes it,
he seems to commit a theft, for he takes another's property. Yet this
seems lawful according to natural equity, as the jurists hold. [*See
loc. cit. in Reply.] Therefore it seems that theft is not always a
sin.

Obj. 3: Further, he that takes what is his own does not seem to sin,
because he does not act against justice, since he does not destroy
its equality. Yet a man commits a theft even if he secretly take his
own property that is detained by or in the safe-keeping of another.
Therefore it seems that theft is not always a sin.

_On the contrary,_ It is written (Ex. 20:15): "Thou shalt not steal."

_I answer that,_ If anyone consider what is meant by theft, he will
find that it is sinful on two counts. First, because of its
opposition to justice, which gi