“Conjecture manifold,
  But, as knowledge, this comes only—­things may be as I behold,
  Or may not be, but, without me and above me, things there are;
  I myself am what I know not—­ignorance which proves no bar
  To the knowledge that I am, and, since I am, can recognize
  What to me is pain and pleasure:  this is sure, the rest—­surmise. 
  If my fellows are or are not, what may please them and what pain,—­
  Mere surmise:  my own experience—­that is knowledge once again."[A]

[Footnote A:  La Saisiaz.]

Experience, then, within which he (and every one else) acknowledges that all his knowledge is confined, yields him as certain facts—­the consciousness that he is, but not what he is:  the consciousness that he is pleased or pained by things about him, whose real nature is entirely hidden from him:  and, as he tells us just before, the assurance that God is the thing the self perceives outside itself,

                  “A force
  Actual e’er its own beginning, operative thro’ its course,
  Unaffected by its end."[A]

[Footnote A:  La Saisiaz.]

But, even this knowledge, limited as it is to the bare existence of unknown entities, has the further defect of being merely subjective.  The “experience” from which he draws his conclusions, is his own in an exclusive sense.  His “thinking thing” has, apparently, no elements in common with the “thinking things” of other selves.  He ignores the fact that there may be general laws of thought, according to which his mind must act in order to be a mind.  Intelligence seems to have no nature, and may be anything.  All questions regarding “those apparent other mortals” are consequently unanswerable to the poet.  “Knowledge stands on my experience”; and this “my” is totally unrelated to all other Mes.

            “All outside its narrow hem,
  Free surmise may sport and welcome!  Pleasures, pains affect mankind
  Just as they affect myself?  Why, here’s my neighbour colour-blind,
  Eyes like mine to all appearance:  ‘green as grass’ do I affirm? 
  ‘Red as grass’ he contradicts me:  which employs the proper term?"[B]

[Footnote B:  Ibid.]

If there were only they two on earth as tenants, there would be no way of deciding between them; for, according to his argument, the truth is apparently decided by majority of opinions.  Each individual, equipped with his own particular kind of senses and reason, gets his own particular experience, and draws his own particular conclusions from it.  If it be asked whether these conclusions are true or not, the only answer is that the question is absurd; for, under such conditions, there cannot be either truth or error.  Every one’s opinion is its own criterion.  Each man is the measure of all things; “His own world for every mortal,” as the poet puts it.

“To each mortal peradventure earth becomes a new machine,
Pain and pleasure no more tally in our sense than red and green."[A]