“It is curious that in political economy, we have not yet succeeded in establishing very general laws, analogous to the fundamental principles of the physico-chemical sciences.”

“I think that the basic intention of the authors, to analyze the economic world, by constructing an analogous fictitious ‘model’, which is sufficiently simplified, so as to allows an absolutely mathematical treatment, is—although not new—sound, and in the spirit of exact sciences. I do not think, however, that the authors have a sufficient amount of mathematical routine and technique, to carry out program out.

I have the impression that the subject is not yet ripe (I mean that it is not yet fully enough understood, which of its features are the essential ones) to be reduced to a small number of fundamental postulates—like geometry, or mechanics (cf. pgs. 77-78). The analogies with thermodynamics are probably misleading (cf. pgs. 69, 85). The authors think that the ‘amortization’ is analogous to ‘entropy’. It seems to me, that if this analogy can be worked out at all, the analogon of ‘entropy’ must be sought in the direction of ‘liquidity’. To be more specific: if the analogon of ‘energy’ is ‘value’ of the estate of an economical subject, then analogon of its thermodynamic ‘free energy’ should be its ‘cash value’.

The technique of the authors to set up and deal with equations is rather primitive, the way, for instance, in which they discuss the fundamental equations (1) and (2) on page 81-85 is incomplete, as they omit to prove that 1: the resulting prices are all positive (or zero), 2: that there is only one such solution. A correct treatment of this particular question, however, exists in the literature. Various other technical details in the setting up of their equations and in their interpretations could be criticized, too. I do not think that their discussion of the ‘stability of solutions’, which is the only satisfactory way to build up a mathematical theory of economic cycles and of crises, is mathematically satisfactory.

The emphasis the authors put on the possibility of states of equilibrium in economics (cf. pgs. 68-69) seems to me to entirely justified. I think that the importance of this point has not always been duly acknowledged. I cannot judge the value of their statistical methods, as they are given in the last part of the book for practical purposes. Their aim is to diagnose the present status of economics, and to lead to forecasts. But I think that the theoretical deduction, which lead to them is weak and incomplete.”

German physicist Albert Einstein's 1946 letter to the Guillaume brothers in support of the economics theories.

“Dr. G. Guillaume, whose family was well known to me in Switzerland, has explained to me a method for mechanized determination of the relative values of the various commodities (in unction of time). I believe that the use of this method may be practical and useful in providing an objective way to obtain an incontestable measure of economic values.”