Dear Mason,

Pardon me if I sound harsh but I would like to 
strongly defend Dupuit's contribution on the 
diminishing marginal utility. Being an 
engineer-economist did not prevent him from 
having pedagogical excellence. Counter to those 
who are not familiar with his writings, he did 
not "imprison thought in mandatory templates". 
For instance, in its brilliant 1849 article, he 
showed the incoherence of Say's arguments (and 
Bordas' too) concerning the notion of utility. In 
this article, you can find why I think he is a 
"total" economist, that is, a scientist who can 
elaborate formal concepts and apply them to real 
economic life,and also show that common business 
practices can be generalized (see his brilliant 
exposure of price discrimination). In addition, 
he was sometimes opposed to his peers of the 
Société d'Economie Politique because he was down 
to earth, counter to Molinari for instance who was imprisoned in his concepts.

I am sure you already read Dupuit's articles. But 
if you doubt, I invite you to read them again so 
that you can be convinced. One more friendly 
advice: try to read them in original version (in French).

Best,

Guy Numa