Simon's argument is simplicity itself--coal, oil and uranium are not resources until they are acted upon by the human intellect. So as population increased, prosperity could increase because more brains were available to work the problem. This works better in free economies than it does in Socialisms or Dictatorships because in free economies all brains are allowed access to the problem. Controlled economies always stagnate because only a few brains are allowed access to the problem. Couldn't be simpler.