Interestingly, necessity is a metaphor when used in contexts
   other than economics. You can thank St Thomas Aquinas for the
   concept of "just price" against usury for its basis.

   Yet, it may or may not follow that necessity is an applicable
   term in other fields in every case.

   The concept may be heavily used in Philosophy, but it is
   fundamentally an economics term and shares the excesses and
   limitations with it.