Note 1112 — Chapter I · : THE HEDONISTS

It is in cases of this kind that figures become handy. If we take two curves, an ascending one to represent the utility of each handful of salt parted with, and a descending one to represent the utility of each handful of rice acquired, the two curves must necessarily intersect, seeing that one is just the inverse of the other. The point of intersection marks the place where the utilities of the two exchanged handfuls are exactly equal.

We must be careful not to confuse matters, however. It is not suggested that the final utilities in the case of the two co-exchangers are equal. There is no common measure by which the desires of different persons can be compared, and no bridge from one to the other. What is implied is that the final utility of both commodities for the same person are the same. The balance lies between two preferences of the same individual. The actual market exchange is just the resultant of all these virtual exchanges.

The Austrian school in its explanation makes use of a hypothesis known as the double limit, which does not seem to be absolutely indispensable, seeing that other economists of the same school—Walras, for example—appear to get on well enough without it. They seem to think of buyers and sellers drawn up in two rows facing one another. Every one of the sellers attributes to the object which he possesses and which he wants to sell a certain utility different from his neighbour’s. Each buyer in the same way attributes to that object which he desires to buy a degree of utility which is different from that which his neighbour puts upon it. The first exchange, which will probably have the effect of fixing the price for all the other buyers and sellers, will take place between the buyer who attributes the greatest utility to the commodity he has to sell, and who is therefore least compelled to sell, and the buyer who attributes the least utility to the commodity he wishes to buy and who is therefore least tempted to buy. At first sight it seems impossible that the party as a whole should be bound by the action of the two individuals who show the least inclination to come to terms. It would be more natural to expect the first move to take place between the seller who is forced to sell and because of his urgency is content with a price of 10s. per bushel, say, and the buyer who feels the strongest desire to buy and who rather than go without would be willing to give 30s. for it. But upon consideration it will be found that the price is indeterminate just because these two are ready to treat at any price. The most impatient individual will surely wait to see what terms the least pressed will be able to make, and it is only natural that those who are nearest one another should be the first to come together. These two co-exchangists who control the market are known as the “limiting couple.”