Sometimes, in reading Bergson, it seems very clear that reality and matter must exclude each other, since one is the negation of the other; and perception and conception, whose object is matter, are not knowledge, because that object is unreal. Moreover, not only is the stuff of reality that _psychic process_ which is life and lapsing time, but there is no stuff more resistant nor more substantial. And in numerous other ways the mutual exclusion of reality and matter seems quite fundamental to Bergsonism. One can never remain long in any security about this, however. If Bergsonism is Platonism reversed, it is natural that the peculiarities of the latter should reappear in some form. Platonic not-being is much too important and too active to be denied a coequal positivity with being. Over and above these “worlds,” moreover, there is that one in which we live, with a third status. Perhaps it is this which is most like Bergsonian matter--“nothing positive, yet not a mere naught”! In the letter from which I have already quoted, Monsieur Bergson wrote me, concerning a previous paper of mine:[123] “You give me the choice between ‘yes’ and ‘no,’ whereas I cannot respond with either, but must mix them. In each particular case, the ‘yes’ and ‘no’ have to be apportioned, and this is just why the philosophy I adhere to is susceptible of improvement and progress. For instance, you find that my premises lead to this conclusion: ‘Matter has no duration; but duration is synonymous with reality; therefore matter is not real.’ But, to my mind, matter has exactly the same reality as rest, which exists only as negation of motion, yet is something other than absolute nothingness. All that is positive in my ‘vital impetus’ is motion; stoppage of this motion constitutes materiality; the latter, therefore, is nothing positive, yet not a mere naught, absolute nothingness being no more stoppage than motion.”