52

POLITICAL  ECONOMY

For  the  twelve  apples  a  week  I  give  Is.  a
week,  but  rather  than  do  without  any  apples
I  would  give  for  the  twelve  Is.  9d.  My
consumer’s  surplus  reckoned  in  money  is,
therefore,  ninepence  on  the  apples.  For
convenience  let  us  call  this  expression  of  the
surplus  in  terms  of  money  monetary  consumer’s ­
  surplus.
To  make  the  notion  with  which  we  have
been  dealing  of  substantial  practical  value,  we
have  to  conceive  of  an  aggregate  monetary
surplus,  with  reference  to  any  commodity,
which  is  made  up  of  the  surpluses  of  a  number
of  different  individuals.  There  is  no  difficulty
in  doing  this,  as  it  is  perfectly  possible  to  add
together  sums  of  money  which  belong  to
different  people,  though  it  is  not  possible  to
conceive  of  the  addition  of  the  things  (preferences) ­
  to  which  these  sums  of  money  refer.
After  performing  the  operation  of  adding
together  consumer’s  surpluses  in  money,
we  must  not,  however,  fall  into  the  error
of  thinking  that  £1  worth  of  one  person’s
consumer’s  surplus  is  the  same  thing  as  £l
worth  of  another  person’s  consumer’s  surplus.
But  this  reservation  notwithstanding,  the
conception  of  a  consumers’  (in  the  plural,
observe)  monetary  surplus  is  of  value  because
it  is  not  unreasonable  to  suppose  that,  other