One, which is the more worthy way, is on account of the
fertility of the country producing an abundance of all things which
are necessary for human life, the other is through the employment
of commerce, through which the necessaries of life are brought from
different places. The former method can be clearly shown to be the
more desirable.... It is more admirable that a State should possess an
abundance of riches from its own soil than through commerce. For the
State which needs a number of merchants to maintain its subsistence
is liable to be injured in war through a shortage of food if
communications are in any way impeded. Moreover, the influx of
strangers corrupts the morals of many of the citizens... whereas,
if the citizens themselves devote themselves to commerce, a door is
opened to many vices. For when the desire of merchants is inclined
greatly to gain, cupidity is aroused in the hearts of many
citizens.... For the pursuit of a merchant is as contrary as possible
to military exertion. For merchants abstain from labours, and while
they enjoy the good things of life, they become soft in mind and their
bodies are rendered weak and unsuitable for military exercises....
It therefore behoves the perfect State to make a moderate use of
commerce.'[1]

[Footnote 1: ii. 3.]

Aquinas, who, as we have seen, recognised the necessity of commerce,
did not condemn all trade indiscriminately, as the Fathers had done,
but made the motive with which commerce was carried on the test of its
legitimacy: 'Trade is justly deserving of blame, because, considered
in itself, it satisfies the greed for gain, which knows no limit, and
tends to infinity. Hence trading, considered in itself, has a certain
debasement attaching thereto, in so far as, by its very nature, it
does not imply a virtuous or necessary end. Nevertheless gain, which
is the end of trading, though not implying, by its nature, anything
virtuous or necessary, does not, in itself, connote anything sinful
or contrary to virtue; wherefore nothing prevents gain from being
directed to some necessary or even virtuous end, and thus trading
becomes lawful. Thus, for instance, a man may intend the moderate gain
which he seeks to acquire by trading for the upkeep of his household,
or for the assistance of the needy; or again, a man may take to trade
for some public advantage--for instance, lest his country lack the
necessaries of life--and seek gain, not as an end, but as payment