The first thing upon which the mediaeval teachers insist is that value is not determined by the intrinsic excellence of the thing itself, because, if it were, a fly would be more valuable than a pearl, as being intrinsically more excellent.[1] Nor is the value to be measured by the mere utility of the object for satisfying the material needs of man, for in that case, corn should be worth more than precious stones.[2] The value of an object is to be measured by its capacity for satisfying men’s wants.  ’Valor rerum aestimatur secundum humanam indigentiam....  Dicendum est quod indigentia humana est mensura naturalis commutabilium; quod probatur sic:  bonitas sive valor rei attenditur ex fine propter quem exhibetur:  unde commentator secundo Metaphysicae nihil est bonum nisi propter causas finales; sed finis naturalis ad quem justitia commutativa ordinet exteriora commutabilia est supplementum indigentiae humanae...; igitur supplementum indigentiae humanae est vera mensura commutabilium.  Sed supplementum videtur mensurari per indigentiam; majoris enim valoris est supplementum quod majorem supplet indigentiam....  Item hoc probatur signo, quia videmus quod illo tempore quo vina deficiunt quia magis indigeremus eis ipsa fiunt cariora....[3]

[Footnote 1:  ’In justitia commutativa non estimatur pretium commutabilium secundum naturalem valorem ipsorum, sic enim musca plus valeret quam totus aurum mundi’ (Buridan, op. cit., v. 14).]

[Footnote 2:  Slater, ‘Value in Theology and Political Economy,’ Irish Ecclesiastical Record, Sept. 1901.]

[Footnote 3:  Buridan, op. cit., v. 14 and 16.  Antoninus of Florence says that value is determined by three factors, virtuositas, raritas, and placibilitas (Summa, ii. 1, 16.)]

The capacity of an object for satisfying man’s needs could not be measured by its capacity for satisfying the needs of this or that individual, but by its capacity for satisfying the needs of the average member of the community.[1] The Abbe Desbuquois, in the article from which we have already quoted, finds in this elevation of the common estimation an illustration of the general principle of the mediaevals, which we have seen at work in their teaching on the use of property, that the individual benefit must always be subordinated to the general welfare.  According to him, it is but one application of the duty of using one’s goods for the common good.  ’In the same way, in allowing the right of exchange—­a right, let us remark in passing, which is but an application of the right of property—­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]