I seem to recall that one of the major points
was that world had suffered a najor nuclear war, and George was sick and dying and on his last legs (literally falling down to die) and he dreamed a better world.
The doctor took his trip in his enhanced machine and saw that the ultimate truth was in fact that the 'real' or 'ultimately truthful' world was dead in a nuclear holocaust, and went mad.
The moral was sort of be happy with what you got and live in the moment.....