My, what a discussion we have generated.  
  
On rationality, I am always surprised that economists think there is   
any thought process associated with rationality.  At best it is a   
Hobbesian pain/pleasure principle.  In practice, whatever people do   
is defined as rational (we don't ask why they do it as psychologists   
would); the question is to explain why anyone similarly situated   
would behave in the same way.  
  
Perhaps we ought to ban "rationality" from the vocabulary of   
economics; it misleads because it implies something that it does not.  
  
Fred Carstensen