John K. Whitaker writes as follows, in part.  
  
"... the analysis of economic phenomena became in the nineteenth century the  
arena in which were contested fundamental issues concerning the mind-body  
distinction and the validity of intuition as a source of knowledge  
additional to observation.  For Jevons   
 (in opposition to John Stuart Mill) only observation counted.  ...  
Observational error was of course to be expected, so that underlying  
functional relations could be observed only probabilistically. Jevons did  
not imply that such an analogue represented absolute truth, but it was all  
that could be attained by scientific observation and reasoning.  Such a  
methodological attitude pervaded his statistical analysis of economic time  
series. ..." (snip)  
   
I hold Prof. Whitaker in high regard, but respectfully call attention to  
Jevons' *Theory of Political Economy*, 5th Ed., Chap. VII, "Theory of  
Capital."  Jevons begins with an Alexander Selkirk example, then says his  
views are "in fundamental agreement with those adopted by Ricardo;" - which  
they are.  Few examples are given, and only after points are conceived a  
priori, and supported by citing previous theorists.  
  
I like Jevons' chapter, but not because it is either original or a  
posteriori.  Rather, it is an alternative exposition of Ricardo, in some  
ways (but not all) clearer.  
  
Maas, of course, is the focused Jevons scholar.  My impression, however, is  
that a generation or two of historians of thought have overstated Jevons'  
departure from his predecessors.  Austrian economists, whom many lump with  
Jevons, refer routinely to part of their capital theory as "Ricardo Effect".  
  
Mason Gaffney