I can't yet trace its proper relations to the aspects of experience of which you do not treat.It needs much building out in the direction of Ethics,Cosmology and Cosmogogy,Psychogenesis,etc. ,before one can apprehend it fully.That I should take it in so much more easily than I did four years ago shows that even at the age of sixty one's mind can grow--a pleasant thought.

It is a work of exquisite genius.It makes a sort of Copernican revolution as much as Berkelet's "Principles" or Kant's "Critical" did,and will probably ,as it gets better and better known,open a new era of philosophical discussion.It fills my mind with all sorts of new questions and hypothses and brings the old into a most agreeable liquefaction.

——William James(Dec.14,1902)