be the
animating motive of every contracting party. The one limitation to
this sweeping rule was in favour of the seller. By a rescript of
Diocletian and Maximian it was enacted that, if a thing were sold
for less than half its value, the seller could recover the property,
unless the buyer chose to make up the price to the full amount.
Although this rescript was perfectly general in its terms, some
authors contended that it applied only to sales of land, because the
example given was the sale of a farm.[1] However, the rescript was
quoted by the Fathers as showing that even the Roman law considered
that contracts might be questioned on equitable grounds in certain
cases.[2] The distinctively Christian notion of just price seems to
have its origin in a passage of St. Augustine;[3] but the notion was
not placed on a philosophical foundation until the thirteenth century.
Even Aquinas, however, although he treats of the just price at some
length, and expresses clear and categorical opinions upon many points
connected with it, does not state the principles on which the just
price itself should be arrived at. This omission is due, not to the
fact that Aquinas was unfamiliar with these principles, but to the
fact that he took them for granted as they were not disputed or
doubted.[4] We have consequently to look for enlightenment upon this
point in writings other than those of Aquinas. The subject can be most
satisfactorily understood if we divide its treatment into two parts:
first, a consideration of what constituted the just price in the sale
of an article, the price of which was fixed by law; and second, a
consideration of what constituted the just price of an article, the
price of which was not so fixed.

[Footnote 1: Hunter, _Roman Law_, p. 492.]

[Footnote 2: Ashley, _op. cit._, p. 133.]

[Footnote 3: 'Scio ipse hominem quum venalis codex ei fuisset oblatus,
pretiique ejus ignarum ideo quiddam exiguum poscentem cerneret
venditorem, justum pretium, quod multo amplius erat nec opinanti
dedisse' (_De Trin._, xiii. 3).]

[Footnote 4: Palgrave, _Dictionary of Political Economy_, tit. 'Justum
Pretium.']

Sec. 2. _The Just Price when Price fixed by Law_.

Regarding the power of the State to fix prices, the theologians and
jurists were in complete agreement. According to Gerson: 'The law
may justly fix the price of things which are sold, both movable and
immovable, in the nature of rents and not in the nature of rents