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  THE 
  PROBLEM 
  OF 
  BODY 
  AND 
  MIND 
  

  

  This 
  amounts 
  to 
  a 
  denial 
  of 
  the 
  existence 
  of 
  the 
  physical 
  

   world 
  and 
  of 
  the 
  possibility 
  of 
  science 
  ; 
  it 
  is 
  the 
  non-pos- 
  

   sumus 
  of 
  solipsism. 
  

  

  (IV) 
  A 
  fourth 
  view 
  common 
  as 
  a 
  working-hypothesis 
  

   at 
  least 
  goes 
  by 
  the 
  name 
  of 
  psycho-physical 
  parallelism. 
  

   It 
  admits 
  the 
  reality 
  of 
  both 
  mental 
  and 
  cerebral 
  processes, 
  

   but 
  regards 
  them 
  as 
  concomitants 
  merely, 
  without 
  inter- 
  

   action, 
  two 
  parallel 
  causal 
  chains, 
  each 
  complete 
  in 
  itself. 
  

   We 
  may 
  think 
  of 
  two 
  watches 
  tied 
  together, 
  keeping 
  perfect 
  

   time, 
  but 
  constructed 
  on 
  different 
  principles 
  and 
  using 
  dif- 
  

   ferent 
  notations. 
  This 
  view 
  was 
  subjected 
  to 
  what 
  seems 
  

   to 
  us 
  destructive 
  criticism 
  in 
  Professor 
  Ward's 
  first 
  course 
  of 
  

   Gifford 
  Lectures 
  on 
  " 
  Naturalism 
  and 
  Agnosticism 
  " 
  ; 
  but 
  

   it 
  is 
  still 
  held 
  by 
  some 
  psychologists 
  of 
  distinction, 
  either 
  

   simply 
  as 
  a 
  convenient 
  way 
  of 
  formulating 
  the 
  facts, 
  or 
  

   with 
  a 
  metaphysical 
  theory 
  behind 
  it 
  namely, 
  an 
  idealistic 
  

   view 
  of 
  material 
  phenomena. 
  

  

  Besides 
  psycho-physical 
  parallelism 
  there 
  are 
  in 
  the 
  field 
  

   three 
  possible 
  theories. 
  One 
  is 
  much 
  favoured 
  by 
  philoso- 
  

   phers 
  (V) 
  the 
  theory 
  of 
  psychical 
  monism. 
  Another 
  view, 
  

   (VI) 
  the 
  soul-theory 
  or 
  animism, 
  does 
  not 
  seem 
  to 
  be 
  fa- 
  

   voured 
  by 
  many 
  philosophers 
  or 
  by 
  many 
  scientific 
  investiga- 
  

   tors, 
  but 
  may 
  be 
  true 
  for 
  all 
  that. 
  The 
  remaining 
  theory, 
  

   much 
  favoured 
  by 
  biologists, 
  is 
  (VII) 
  the 
  two-aspect 
  or 
  iden- 
  

   tity 
  hypothesis. 
  It 
  seems 
  to 
  us 
  that 
  each 
  of 
  these 
  theories 
  has 
  

   its 
  particular 
  advantages 
  and 
  its 
  particular 
  difficulties, 
  and 
  

   that 
  a 
  decision 
  must 
  at 
  present 
  be 
  left 
  with 
  the 
  individual 
  

   according 
  to 
  his 
  personal 
  experience. 
  In 
  our 
  judgment 
  the 
  

   biological 
  facts 
  mostly 
  favour 
  the 
  two-aspect 
  theory, 
  but 
  we 
  

   have 
  no 
  assurance 
  that 
  it 
  is 
  the 
  most 
  valid. 
  

  

  (V) 
  Psychical 
  Monism. 
  According 
  to 
  the 
  doctrine 
  of 
  

   psychical 
  monism, 
  conscious 
  process 
  is 
  the 
  only 
  reality, 
  and 
  

  

  