it is felt that it would be to give up the whole task to admit a principle of original and arbitrary energy as a factor in the explanation. We constantly hear that this is materialism, and for one who does not distinguish between science and metaphysics it is materialism. But that distinction should, in the light of present-day discussion, be fairly obvious.
Avenarius undertakes to write a psychology of the processes of knowledge. Whether his psychology is a good one is a point for psychologists to decide. The important thing for us to notice is that the 'Kritik der Reinen Erfahrung' is psychology.
There is at the outset a certain fund of information to build upon. Whatever our metaphysic may be, we 'know' in psychology that consciousness depends upon processes in the brain of some sort, that the nervous system is responsive to stimuli, that the whole body, and the nervous system as part of it, is constantly engaged in breaking down tissue, and is in need of appropriate nourishment and of periodical repose. We know that the organism and its parts are capable of exhaustion, and, within limits, of recovery from exhaustion. There is a teleological aspect of the reactions which the organism makes to a great many stimuli. This aspect it is which has given to the soul concept such a stubborn foothold in psychology. But though we are unable to make a psychological use of this concept, we may not, therefore, overlook the facts which it was intended to explain. We can observe, too, a certain rhythmical character in life as a whole and in many particular processes. The alternation of day and night occasions regular intervals of work and rest, with points of maximal vigor and fatigue, and transitions back and forth between them.
We are assured also that there is a region which we call the central nervous system which receives stimuli and determines reactions. We know, too, that the physiological system acquires habits and is capable of acquiring skill. These things depend upon processes of some sort in an organ, the brain, but upon what processes in particular we know hardly at all.
Can we conceive an organ of such a type as to account for enough of such phenomena as to make it a useful concept for psychological purposes? Avenarius thinks we can, and he proceeds to describe a central nervous system with such characters as would explain, he thinks, a great many phenomena in a psychological way.
Avenarius describes a way of apperceiving the central nervous system. Certain phenomena being given, there is wanted a concept to make them intelligible. Avenarius is, in so far, in the same position as the one who elaborates a system of atomic relations to account for chemical phenomena.
The central nervous system is called by Avenarius the System
