Such ideas were a natural basis for the Church's
attempt to control the issues of war and peace; and if we remember these
ideas, we shall acquit the Church of any impracticable quixotism.

The attempt to control trade and commerce was no less lofty and no less
arduous. It is perhaps still easier to stop war than to stop
competition; and yet the Church made the attempt. The Christian law of
love was set against the economic law of demand and supply. It was
canonical doctrine that the buyer should take no more, and the seller
offer no less, than the just price of a commodity--a price which would
in practice depend on the cost of production. The rule for prices was
also the rule for wages: the just wage was the natural complement of the
just price. The prohibition of usury and of the taking of interest was
another factor in the same circle of ideas. If prices and wages are both
to be returns for work done, and returns of an exact equivalence, then,
on the assumptions which the canonists made--that the usurer does no
work, and that his loan is unproductive of any new value--it necessarily
follows that no return is due, or can be justly paid, for the use of
borrowed money. Work is the one title of all acquisition, and all
acquisition should be in exact proportion to the amount of work done.
This is the basic principle, and it is the principle of the Divine Law:
_In sudore frontis tuae comedes panem tuum_. Once more, therefore, and
once more in an unpromising and intractable material, we find the Church
seeking to enforce the unity of the Christian principle and to reduce
the Many to the One. In the same way, and from the same motive, that
private war was to be banished from the feudal class in the country,
competition--the private war of commerce--was to be eliminated from the
trading classes in the towns. Nor was the attack on competition, any
more than the attack on war, so much of a forlorn hope as it may seem to
a modern age. Even to-day, custom is still a force which checks the
operation of competition, and custom covered a far greater area in the
Middle Ages than it does to-day. The rent of land, whether paid in
labour or in kind, was a customary rent; and in every mediaeval
community the landed class was the majority. It was an easy transition
from fixed and customary rents to the fixing of just prices for
commodities and services. Lay sentiment supported clerical principle.
Guilds compelled their members to sell commo