118 Irving Fisher — ^fatliematical investigations 



they have once been observed; but it cannot by any process of its 

 own determine those ratios; for quantitative conclusions imply quan- 

 titative premises and these are wanting. There is then no future 

 for this kind of study, and it is only waste of intellectual power to 

 pursue it." [What a "therefore"! Why require mathematics to 

 predict prices in order to be admitted into g'ood society with the his- 

 torical school ? No mathematical economist has ever tried to do 

 this. Dr. Ingram does not discuss what mathematics has done or 

 attempted, but complai]is loudly that it cannot do everything and 

 therefore has no future.] 



jRabherid^ in speaking of Prof. Pantaleoni's Principi di Economia 

 Pura says: '* As a monument of abstract logic, it bears fresh witness 

 to the unusual qualities of the author's genius; but it is based on a 

 method which, frankly speaking, I consider dangerous. In the face 

 of pressing practical problems of every kind, both in production and 

 in distribution, economic thought is drawn off into the field of bar- 

 ren abstractions. Under an attractive semblance of mathematical 

 accuracy these abstractions conceal much that is really false ; for 

 they do not correspond in the least to the complexity of concrete 

 facts. While they distract the student with an imaginary logical 

 construction, they lessen his interest in that positive study which 

 tells us what is, whereas logic by itself gives us only what is 

 thought. Thus in last result they deprive economic science of that 

 great practical importance which it should have in society." [I am 

 not acquainted with Prof. Pantaleoni's book nor with any Italian 

 writer. As to the criticism on mathematical method, however, I 

 may say that experience in other sciences shows that " in face of 

 many practical problems" it is wisest to "draw off thought" for a 

 time to pure theory. Before solving the problems of cannon pro- 

 jectiles it is best to solve the problem of projectiles in general. 

 Before an engineer is fit to build the Brooklyn bridge or to pro- 

 nounce on it after it is built it is necessary to study mathematics, 

 mechanics, the theory of stress and of the natural curve of a hang- 

 ing rope, etc., etc. So also before applying political economy to 

 railway rates, to the jjroblems of trusts, to the explanation of some 

 current crisis, it is best to develop the theory of pol. econ. in general. 

 When these special "practical problems" are examined the mathe- 

 matical instrument will, I believe, often be the one to get the best 

 results. 



I am far from denying, however, that some mathematical econo- 

 mists have exhibited a "false accuracy." It has been due to 



* Economics in Italy, Prof. Qgo Eabberio, Pol. Sci. Quart., Sept. 1891, p. 462. 



