“ The philosopher begins with what Avenarius calls the “natural world-conception.” But this natural world-conception leads to contradictions and the evil spirit of speculation leads us in a circle through the barren fields of idealism. Avenarius asks: “Is the world really of such a nature that it appears unitary and consistent only to the superficial thinker, while it leads every one astray who attempts to grasp it more precisely in its entirety—the more so the more consistently the thinker proceeds?” ”

“ The data of experience are not mere feelings, not mere subjectivity, as is maintained by the idealist; nor are they mere objectivity, as is maintained by the ingenuous realist; the data of experience are states of subject-objectness, they are feelings of a certain kind possessing objective significance, and the ideas subject as well as object are abstractions made in a late stage of mental development from this one inseparable whole of subject-objectness (see The Monist I, No. 1, pp. 78-79) . ”

“ Avenarius says in a note (p. 132) , “The question should not be ‘Why do we believe in the reality of an external world?’ but ‘Why did we not believe that the external world is real?’” We should say that neither question is admissible. We should first ask: What do we mean by real? Reality is the sum total of our experiences, including the meaning of sensations and ideas, and finds its special application in their reliability. ”