which produce changes in consciousness, the greater the one change the greater the other. And although the one series of changes is quantitative and the other qualitative, we do speak of a more and less, and carry on a good deal of comparison in the region of qualities. We have, in any case, a physiological series, and dependent upon this a series of mental states, or rather we have a continuous nervous process and a continuous stream of consciousness depending upon the former, and these continuous processes we can break up into parallel lengths, called vital series. The physiological series is called the Independent Vital Series, the series in consciousness is called the Dependent Vital Series.
It is unfortunate that the method of exposition chosen by Avenarius makes it appear superficially that the dependent vital series is deduced from the concept of the independent series, together with the general presuppositions, and that therefore nothing about the dependent series can be any better established than the concept of the independent series.
Obviously, however, the dependent series is a movement in consciousness which can be observed, and it is to account for these series of conscious states, which are data of experience, that the physiological series is assumed.
In the above case of an attention-process as a dependent vital series, three stages can be observed: first, the appearance of the problem, the awakening of interest and the consequent feeling of restlessness and dissatisfaction if the solution does not immediately appear. This is the 'Initial' stage; then comes the continued effort to solve the problem, the 'Medial' stage; and finally the appearance of the solution, characterized by satisfaction, abating anxiety, the settling down upon an opinion or a cognition. This is the 'Final' stage. Corresponding to these three stages of the dependent series are three stages of the independent series,—the appearance of the vital difference and a departure of the system C from stability, the continuance for a longer or shorter time with an approximately constant vital difference, and then the reduction of the vital difference to zero, with consequent return to stability.
The system C maintains itself by getting back to stability after disturbances. This functional activity can be performed in a way that is better or worse for the life of the system C itself, that is, we can conceive an ideal system C. Such an organ would, after any disturbance, return to stability with the shortest interval of a vital series. This would be accomplished if the system C were trained to recover stability by means of well-learned and completely habitual vital series, that is, if the system C by virtue of its liability to habit has learned to recover stability with maximum facility.
