constitute the substantial value of goods, and then construe market value to be an approximate and uncertain expression of this substantial fact. The direction in which the argument runs is rather the reverse of this. The point of departure is taken from the range of market values and the process of bargaining by which these values are determined. This latter is taken to be a process of discrimination between various kinds and degrees of discomfort, and the average or consistent outcome of such a process of bargaining constitutes normal value. It is only by virtue of a presumed equivalence between the discomfort undergone and the concomitant expenditure, whether of labor or of wealth, that the normal value so determined is conceived to be an expression of the productive force that goes into the creation of the valuable goods. Cost being only in uncertain equivalence with sacrifice or discomfort, as between different persons, the factor of cost falls into the background; and the process of bargaining, which is in the foreground, being a process of valuation, a balancing of individual demand and supply, it follows that a law of reciprocal demand comes in to supplant the law of cost. In all this the proximate causes at work in the determination of values are plainly taken account of more adequately than in earlier cost-of-production doctrines; but they are taken account of with a view to explaining the mutual adjustment and interrelation of elements in a system rather than to explain either a developmental sequence or the working out of a foreordained end. This revision of the cost-of-production doctrine, whereby it takes the form of a law of reciprocal demand, is in good part effected by a consistent reduction of cost to terms of sacrifice,--a reduction more consistently carried through by Cairnes than it had been by earlier hedonists, and extended by Cairnes's successors with even more far-reaching results. By this step the doctrine of cost is not only brought into closer accord with the neo-hedonistic premises, in that it in a greater degree throws the stress upon the factor of personal discrimination, but it also gives the doctrine a more general bearing upon economic conduct and increases its serviceability as a comprehensive principle for the classification of economic phenomena. In the further elaboration of the hedonistic theory of value at the hands of Jevons and the Austrians the same principle of sacrifice comes to serve as the chief ground of procedure. * * * * *