202

POLITICAL  ECONOMY

A  with  its  produce  of  60  bushels  will  rise  to  45,
that  is  60  minus  15,  on  the  assumption  that
the  whole  of  the  lowest  quality  of  land  is  not
in  use.  The  significance  of  this  assumption
will  be  brought  out  in  due  course.
We  may  pause  to  underscore  what  is
outstanding  in  this  reasoning,  namely,  that
it  is  the  operation  of  the  law  of  substitution, ­
  or  indifference,  among  competing
persons  which  brings  about  the  payment  of
rent  in  the  circumstances  supposed.  Payments ­
  are  made  for  land  because  effective
tendencies  to  substitute  what  is  lying  idle
for  what  is  used,  and  what  is  cheap  for  what
is  dear,  are  at  work.  These  effective  tendencies ­
  at  first  create  the  rent,  and  then  lever  it
up  until  it  becomes  such  in  amount  that  any
further  substitution  is  a  matter  of  indifference.
So  we  may  affirm  that  the  rent  of  land  is
the  payment  which  equalises  the  earnings  of
cultivators  of  the  same  capacity,  thus  leaving
them  indisposed  to  substitute  one  piece  of
land  for  another.
In  order  to  complete  our  theory  in  its  first
rough-hewn  form  it  is  necessary  to  consider
what  would  happen  if  the  whole  of  the  land
were  absorbed  and  the  population  still  grew.
Let  a  state  of  affairs  be  given  in  which  all  the
land  is  in  use,  but  the  worst  only  just  in  use,