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