Now we are sure that the nervous system is subject to habit, and that this is one of the factors which is most important in making life well organized, in simplifying the mental outlook, in making experience coherent and developing a consistent will. Our point of view obliges us, therefore, to assume a parallel physiological development.
Certain independent (physiological) vital series thus become habitual, and the functional excellence of the system C is in proportion as the fund of habitual series is adequate to all the reactions of the system. Such an 'eingeübte' series Avenarius calls a 'vital series of the first order.' Other series with a more or less novel character he calls 'vital series of a higher order.' Evidently the functional development of the system C lies in the reduction of series of higher orders to series of the first order. This means the gradual introduction of order into the behavior of the system C by means of its own education, if we may so describe it.
By habit we reduce the complex environment to its simplest terms. We learn to ignore large masses of it, or rather we react upon various manifolds according to certain constant characters or values which we find in them. If we translate this into physiological terms, it gives us a sort of physiological selection. The nervous system has become responsive to certain selected portions of its environment. That is, the education of the system C has been controlled by certain R-values to the exclusion of others. This concept of physiological habit is of the first importance in the theory of Avenarius, but it is so important because the fact of habit is of such great importance in life.
The consequence of habit is that experience becomes less and less diversified. All sorts of E-values no longer occur. In its effects upon experience, growth by habit is a process of exclusion, which, so far as the character of the system C is concerned, could go on indefinitely. It is a process by which the mind comes to give a final definite character to the manifold presented to it by the world, —a process by which a maximum experience of the world expresses itself in a resulting apperception of the world. This final apperception of the world depends upon the possession of a predicate which is applicable to every fact which experience testifies to as existent, and this means, in the terminology of Avenarius, that a final stage of the system C has been found by which any vital difference may be annulled. By virtue of its capacity for acquiring habits, the system C has found an answer to the question, 'What is everything?'
This idea of a limiting stage of the process of progressive determination of experience is, of course, only an idea, but it is not,
