Edgeworthian Exchange

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"It may be said that in pure economics there is only one theorem, but that it is a very difficult one: the theory of bargain in a wide sense."

(Francis Ysidro Edgeworth, 1889, "On the Application of Mathematics to Political conomy", Nature)

"Equilibrium is attained when the existing contracts can neither be varied without recontract with the consent of the existing parties, nor by recontract within the field of competition. The advantage of this general method is that it is applicable to the particular case of imperfect competition where the conceptions of demand and supply at a price are no longer appropriate."

(Francis Y. Edgeworth, Mathematical Psychics, 1881: p.31)

“Now the rationale for this deduction, the reason why the complex play of competition tends to a simple uniform result - what is arbitrary and indeterminate in contract between individuals becoming extinct in the jostle of competition -- is to be sought in a principle which pervades all mathematics, the principle of limit, or law of great numbers as it might perhaps be called.”

(Francis Ysidro Edgeworth, "The Rationale of Exchange", Journal of Statistical Society of London, 1884: p.164)

"Francis is a charming fellow, but you must be careful with Ysidro!"

(Alfred Marshall, as attributed in J. M. Keynes, Essays in Biography, 1933: p.236).

"I have been particularly impressed by one thing, and that is that economists who are mediocre mathematicians, like Jevons, have produced excellent economic theory, whereas some mathematicians who have an inadequate knowledge of economics, like Edgeworth, ...talk a lot of nonsense."

(Léon Walras, "Letter to Perozzo, March 18, 1890")

"This book shows clear signs of genius, and is a promise of great things to come...It will be interesting, in particular, to see how far he succeeds in preventing his mathematics from running away with him out of sight of the actual facts of economics."

(Alfred Marshall, 1881, "Review of Edgeworth's Mathematical Psychics", The Academy)

"It is not the mathematics which is running away with Edgeworth but his love for the classics. Edgeworth's arguments satisfy today's standard of rigor."

(Werner Hildenbrand, 1993, "Francis Ysidro Edgeworth: Perfect competition and the core", European Economic Review)