m, medium, and minimum
just price; and that any price between the maximum and minimum was
valid, although the medium was to be aimed at as far as possible.

[Footnote 1: II. ii. 77, 1, ad. 1.]

[Footnote 2: _De Cont. Sim._, 58.]

[Footnote 3: _De Cont._, ii. 11.]

[Footnote 4: _Op. cit._, IV. xv. 10.]

The price fixed by common estimation was therefore the one to be
observed in most cases, and it was at all times a safe guide to
follow. If, however, the parties either knew or had good reason to
believe that the common estimation had fixed the price wrongly,
they were not bound to follow it, but should arrive at a just
price themselves, having regard to the various considerations given
above.[1]

[Footnote 1: Nider, _De Cont. Merc._ ii.: 'Si vero scit vel credit
communitatem errare in estimatione pretii rei; tunc nullo modo debet
eam sequi; quia etiam si reciperet verum et justum pretium, tamen
faceret contra conscientiam.']

It did not make any difference whether the price was paid immediately
or at some future date. To increase the price in return for the giving
of credit was not allowed, as it was deemed usurious--as indeed it
was. It was held that the seller, in not taking his money immediately,
was simply making a loan of that amount to the buyer, and that to
receive anything more than the sum lent would be usury. Aquinas is
quite clear on this point. 'If a man wish to sell his goods at a
higher price than that which is just, so that he may wait for the
buyer to pay, it is manifestly a case of usury; because this waiting
for the payment of the price has the character of a loan, so that
whatever he demands beyond the just price in consideration of this
delay, is like a price for a loan, which pertains to usury. In like
manner, if a buyer wishes to buy goods at a lower price than what is
just, for the reason that he pays for the goods before they can
be delivered, it is likewise a sin of usury; because again this
anticipated payment of money has the character of a loan, the price of
which is the rebate on the just price of the goods sold. On the other
hand, if a man wishes to allow a rebate on the just price in order
that he may have his money sooner, he is not guilty of the sin of
usury.'[1] If, however, the seller, by giving credit, suffered any
damage, he was entitled to be recompensed; this, as we shall see, was
an ordinary feature of usury law. It could not be said that the price
was raised. The price r