point of view some reports of experience may be true reports of fact while others are not, but this is to say that experience is not necessarily valid experience. And the charge of incorrect observation must always be a character of another experience.
Now this cognitive experience can be made the object of scientific study. To say that an explanation of cognitive experience must be wholly futile because the judgments which state the explanation will themselves express only other cognitive experience is to misunderstand the purpose. The real effort in a psychophysical account of pure experience is not so much to get back of pure experience, as to get a larger acquaintance with it— to extend cognitive experience so as to include judgments about cognitive experience itself. Of course we explain cognitive experience by reducing it to cognitive experience, but this is our way of getting a fuller and richer cognitive experience. Whether we employ psychophysical concepts or mere introspection is a question of method. Because psychology makes extensive use of psychophysical concepts, and speaks of an outer world as the source of stimuli, psychology is not therefore metaphysics. Psychology has its point of view and its favorite method. Its data are observed data. Its aim is to observe other data. Any instruments which lead to richer observations are legitimate, and do not commit the psychologist to a metaphysic just because the aim is to come around again to another observation, and not to rest in the concept of an ultimate ground of phenomena which can not be observed.
This, however, is the distinction between description and explanation as ultimate goals. We may say that the aim of science is the widest possible acquaintance with phenomena, where the word phenomena does not imply the metaphysical distinction of appearance and reality. Methods of observation appropriate to different regions of phenomena, and points of view for the apperception and orderly synthesis of phenomena, are developed. In the course of this work of observation and description various points of view are elaborated which have the function of explaining phenomena rather than of synthesizing and describing them, although both explanation and description may be accomplished. A point of view which both explains and describes is the principle of evolution. A point of view which as yet can be said only to explain is the reference of mental states to physical processes in the brain as the ground of consciousness. This latter point of view it is which has brought forth the much-discussed concept of psychophysical parallelism. At the risk of digression, a brief orientation on this concept will clear the ground for considering the application which Avenarius has made of it in his 'Kritik der Reinen Erfahrung.'