Another perspective on economics as a theory of choice is gained by   
remembering that neoclassical choice theory is a statement of commercial   
logic, where there is a numeraire and a clear priority.  In the 15th and   
16th centuries in Western Europe, the innovation of double-entry   
bookkeeping and spreading use of a standard money as a numeraire made it   
possible to measure well costs and revenues.  In the case of commercial   
establishments in a commercial system, survival requires that revenues   
equal or exceed costs over some reasonable period of time.  Rationality   
can be precisely defined.   This logic spread to be used by households,   
family farms, government agencies, etc. and as it has spread this   
commercial logic has come to be thought of as Rationality.  However, there   
are many forms of rationality, which is to say many bases for purposful   
action.  In some cases there is simply no easily employed numeraire and in   
many cases there may be multiple goals.  Fortunately, not all of life is a   
simple matter of applying a commercial logic.  
  
Anne Mayhew