﻿ISAAC 
  NEWTON 
  ^EINSTEIN 
  207 
  

  

  of 
  the 
  field, 
  which 
  corresponds 
  to 
  Newton's 
  law 
  of 
  force. 
  Only 
  when 
  

   this 
  aim 
  has 
  been 
  fully 
  attained 
  can 
  we 
  speak 
  of 
  a 
  pure 
  theory 
  of 
  

   fields. 
  

  

  Newton's 
  mechanics 
  prepared 
  the 
  way 
  for 
  the 
  theory 
  of 
  fields 
  in 
  a 
  

   yet 
  more 
  formal 
  sense. 
  The 
  application 
  of 
  Newton's 
  mechanics 
  to 
  

   continously 
  distributed 
  masses 
  led 
  necessarily 
  to 
  the 
  discovery 
  and 
  

   application 
  of 
  partial 
  differential 
  equations, 
  which 
  in 
  turn 
  supplied 
  

   the 
  language 
  in 
  which 
  alone 
  the 
  laws 
  of 
  the 
  theory 
  of 
  fields 
  could 
  be 
  

   expressed. 
  In 
  this 
  formal 
  connection 
  also 
  Newton's 
  conception 
  of 
  

   the 
  differential 
  law 
  forms 
  the 
  first 
  decisive 
  step 
  to 
  the 
  subsequent 
  

   development. 
  

  

  The 
  whole 
  development 
  of 
  our 
  ideas 
  concerning 
  natural 
  phenom- 
  

   ena, 
  which 
  has 
  been 
  described 
  above, 
  may 
  be 
  conceived 
  as 
  an 
  organic 
  

   development 
  of 
  Newton's 
  thought. 
  But 
  while 
  the 
  construction 
  of 
  the 
  

   theory 
  of 
  fields 
  was 
  still 
  actively 
  in 
  progress, 
  the 
  facts 
  of 
  heat 
  radia- 
  

   tion, 
  spectra, 
  radioactivity, 
  and 
  so 
  on, 
  revealed 
  a 
  limit 
  to 
  the 
  em- 
  

   ployment 
  of 
  the 
  whole 
  system 
  of 
  thought, 
  which, 
  in 
  spite 
  of 
  gigantic 
  

   successes 
  in 
  detail, 
  seems 
  to 
  us 
  to-day 
  completely 
  insurmountable. 
  

   Many 
  physicists 
  maintain, 
  not 
  without 
  weighty 
  arguments, 
  that 
  in 
  

   face 
  of 
  these 
  facts 
  not 
  only 
  the 
  differential 
  law 
  but 
  the 
  law 
  of 
  causal- 
  

   ity 
  itself 
  — 
  hitherto 
  the 
  ultimate 
  basic 
  postulate 
  of 
  all 
  natural 
  science 
  

   — 
  fails. 
  

  

  The 
  very 
  possibility 
  of 
  a 
  spatio-temporal 
  construction 
  which 
  can 
  

   be 
  clearly 
  brought 
  into 
  consonance 
  with 
  physical 
  experience 
  is 
  denied. 
  

   That 
  a 
  mechanical 
  system 
  should 
  permanently 
  admit 
  only 
  discrete 
  

   values 
  of 
  energy 
  or 
  discrete 
  states 
  — 
  as 
  experience, 
  so 
  to 
  say, 
  directly 
  

   shows 
  — 
  seems 
  at 
  first 
  hardly 
  deducible 
  from 
  a 
  theory 
  of 
  fields 
  work- 
  

   ing 
  with 
  differential 
  equations. 
  The 
  method 
  of 
  De 
  Broglie 
  and 
  

   Schrodinger, 
  which 
  has, 
  in 
  a 
  certain 
  sense, 
  the 
  character 
  of 
  a 
  theory 
  

   of 
  fields, 
  does 
  deduce, 
  on 
  the 
  basis 
  of 
  differential 
  equations, 
  from 
  a 
  

   sort 
  of 
  considerations 
  of 
  resonance 
  the 
  existence 
  of 
  purely 
  discrete 
  

   states 
  and 
  their 
  transition 
  into 
  one 
  another 
  in 
  amazing 
  agreement 
  with 
  

   the 
  facts 
  of 
  experience 
  ; 
  but 
  is 
  has 
  to 
  dispense 
  with 
  a 
  localization 
  of 
  

   the 
  mass-particles 
  and 
  with 
  strictly 
  causal 
  laws. 
  Who 
  would 
  be 
  .so 
  

   venturesome 
  as 
  to 
  decide 
  to-day 
  the 
  question 
  whether 
  causal 
  law 
  and 
  

   differential 
  law, 
  these 
  ultimate 
  premises 
  of 
  Newton's 
  treatment 
  of 
  

   nature 
  must 
  definitely 
  be 
  abondoned 
  ? 
  

  

  