I've noticed economists' frequent use of the phrase, "writing down a   
model."  Many use it to describe the process of formulating an economic   
theory in a few mathematical equations, and for many economists "writing   
down a model" is the only kind of "theorizing" they would think of   
doing.  The phrase seems to have become more than a literal description of   
formulating a model--it's also become a catchword for a particular kind of   
theorizing.  
  
Can anyone shed light on the origin, or earliest uses, of the phrase, in   
economics?  Will someone speculate on the significance of "writing" as   
opposed to some other action?  Finally, do social scientists other than   
economists use the phrase?  (I know that natural scientists do.)  
  
Roger E. Bolton