_A Modern Variation of the Mediæval Theory_ In spite of its fundamental impossibility, the concept of exchange-equivalence still haunts the minds of certain Catholic writers.[222] They still strive to get a formula to express equality between labour and remuneration. Perhaps the best known and least vulnerable of the attempts made along this line is that defended by Charles Antoine, S.J.[223] Justice, he declares, demands an objective equivalence between wages and labour; and objective equivalence is determined and measured by two factors. The remote factor is the cost of decent living for the labourer; the proximate factor is the economic value of his labour. The former describes the _minimum_ to which the worker is entitled; the latter comprises perfect and adequate justice. In case of conflict between the two factors, the first is determinative of and morally superior to the second; that is to say, no matter how small the economic value of labour may _seem_ to be, it never can descend below the requisites of a decent livelihood. Now, neither of these standards is in harmony with the principle of exchange-equivalence, nor capable of serving as a satisfactory criterion of wage justice. Father Antoine argues that labour is always the moral equivalent of a decent livelihood because the worker expends his energies, and gives out a part of his life in the service of his employer. Unless his wage enables the labourer to replace these energies and conserve his life, it is not the equivalent of the service. If the wage falls short of this standard the labourer gives more than he receives, and the contract is essentially unjust. In this conception of equivalence, energy expended, instead of cost of living, becomes the term of comparison and the common measure of labour and remuneration. Energy expended is, however, technically incapable of providing such a common standard; for it does not measure both related terms in the same way. The service rendered to the employer is the _effect_ rather than the equivalent of the energy expended; and the compensation is a _means_ to the replacement of this energy rather than its formal equivalent. Moreover, the formula does not even furnish an adequate rational basis for the claim to a decent minimum wage. A wage which is merely adequate to the replacement of expended energy and the maintenance of life, is really inadequate to a decent livelihood. Such compensation would cover only physical health and strength, leaving nothing for intellectual, spiritual, and moral needs. As Father Antoine himself admits and contends, the latter needs are among the elements of a decent livelihood, and a wage which does not make reasonable provision for them fails to comply with the minimum requirements of justice.