I'm working on a paper on what counts as evidence for 'creative destruction.'  In the
paper, I intend to have a few paragraphs on the phrase "to fix ideas" that is commonly
used in formal theorizing and assumption-making.  (There was a revealing and intense
exchange at the International Schumpeter Society meetings in France last summer between
Richard Nelson, Phillipe Aghion, and William Baumol, in which Aghion used the phrase "fix
ideas" a couple of times in his defense of formal modelling; as against Nelson's advocacy
of a thicker, more tolerant, methodology.)
  
I'm not aware of any discussions of this phrase in the history of economic thought, or
economic methodology, literatures, but I easily could have missed something.  Does anyone
know the origins of the phrase?  E.g., did the economists who use it, borrow it from some
other discipline?  And are there any methodology discussions of how the phrase gets used,
and whether the use is sound?
  
Art Diamond