DEMAND

45

ence  of  income  from  the  one  line  of  expenditure
to  the  other,  so  long  as  the  two  marginal
utilities  differed.  Hence,  I  should  try  to  get
the  two  marginal  satisfactions  equal.  What  is.
true  in  this  matter  of  two  things  is  evidently
true  of  any  number.
There  is  a  reason  for  most  things,  even
for  this  law’s  profusion  of  names.  Each  name
is  appropriate  and,  in  the  absence  of  any
fixation  of  terminology  by  convention,  some
writers  have  favoured  one  name  and  some
another.  The  law  is  called  the  law  of  equimarginal ­
  returns  because  when  it  is  observed
equi-marginal  returns  result.  It  is  called  the
aw  of  substitution  because  the  end,  equimarginal ­
  returns,  is  attained  by  the  process,
of  substitution  already  described.  It  is  called
the  law  of  indifference  because,  when  it  is
observed,  a  person’s  scheme  of  expenditure
is  so  devised  that  it  is  a  matter  of  indifference
to  him  whether  he  spends  a  minute  accession
of  income  on  any  one  thing  or  on  any  other.
Before  concluding  our  study  of  demand  and
expenditure,  a  few  words  are  needed  to  indicate
the  extent  to  which  the  laws  of  demand  and
expenditure  hold  in  actual  practice.  It  may
have  been  gathered  from  the  exposition  above
that  the  individual  is  unceasingly  engaged
in  balancing  the  utilities  of  different  courses