It  is  unjust  for  all  that;  for,  although  the  calculation
has  positively  been  made,  still  the  child  knows  nothing
of  the  operations  to  which  he  has  had  recourse;  then
how  ask  him  to  repeat  them  with  other  figures?^

I  pass  now  to  a  class  of  examples  in  which  we  shall
find  common  sense  showing  still  more  evidently  its
complete  insufficiency;  it  no  longer  merely  denies  the
truth,  it  declares  it  to  be  absurd.  No  one  in  this  day
is  ignorant  of  the  fact  that  the  earth  is  not  the  centre
of  the  universe,  nor  even  of  the  solar  system,  and  that
it  is  round  and  inhabited  in  almost  every  part.^  But
these  facts  fly  in  the  face  of  the  most  elementary  com-
mon sense.     If  you  explain  clearly  to  the  first  child

*  A  similar  observation  has  been  made  by  Morgan,  Introduction
to  Comparative  Psychology,  London  and  New  York,  1896,  p.  229.
He  solves  the  problem  by  supposing  the  intervention  of  a  marginal
consciousness.  Apart  from  the  words,  the  point  of  view  of  Morgan
is  the  same  as  mine.
^  The  facts  that  militate  against  the  theory  of  Laplace  are  not  to  be
taken  into  account  here,  for  they  do  not  touch  upon  the  sphericity  of
the  terrestrial  globe.  See  a  few  words  on  these  objections  in  Certitude
Logique,  G.  Milhaud,  second  ed.,  Paris,  F.  Alcan,  1898,  pp.  104-106.
