--and in allowing
it as a means of life necessary to everybody, nature does not lose
sight of the universal destination of economic goods. One conceives
then that the variations of exchange are not permitted to be left
to the arbitrary judgment of a single man, nor to be affected by the
whims and abuses of individuals; that value is defined in view of the
general good. The exchange value, as it is in the general or social
order, proceeds from the judgment of the social environment (_milieu
social_).'[2]

[Footnote 1: 'Indigentia istius hominis vel illius non mensurat
valorem commutabilium; sed indigentia communis eorum qui inter se
commutare possunt,' Buridan, _op. cit._, v. 16. 'Prout communiter
venditur in foro,' Henri de Gand, _Quod Lib._, xiv. 14; Nider, _De
Cont. Merc._, ii. 1.]

[Footnote 2: 'La Justice dans l'Echange,' _Semaine Sociale de France_,
1911, p. 168.]

The writers of the Middle Ages show a very keen perception of the
elements which invest an object with the value which is accorded to
it by the general estimation. In Aquinas we find certain elements
recognised--'diversitas loci vel temporis, labor, raritas'--but it is
not until the authors of the fourteenth and fifteenth centuries that
we find a systematic treatment of value.[1] First and foremost there
is the cost of production of the article, especially the wages of all
those who helped to produce it. Langenstein lays down that every one
can determine for himself the just price of the wares he has to sell
by reckoning what he needs to support himself in the status which he
occupies.[2] According to the _Catholic Encyclopaedia_,[3] the
just price of an article included enough to pay fair wages to the
worker--that is, enough to enable him to maintain the standard of
living of his class. This, though not stated in so many words
by Aquinas, was probably assumed by him as too obvious to need
repetition.[4] 'The cost of production of manufactured products,' says
Brants, 'is a legitimate constituent element of value; it is according
to the cost that the producer can properly fix the value of his
product and of his work.'[5]

[Footnote 1: Brants, _op. cit._, p. 69.]

[Footnote 2: _De Cont._, quoted by Roscher, _Geschichte_, p. 20.]

[Footnote 3: Tit. 'Political Economy.']

[Footnote 4: Palgrave, _Dictionary_, tit. 'Justum Pretium.']

[Footnote 5: Brants, _op. cit._, p. 202.]

The cost of the labour of production was, however, by no means the
only