knowledge, and similarly as having spatial limits that may be transcended in imagination and thought. On the other hand, from the relative point of view the tree is considered not in and for itself, but in itself and for me. It is then perceived that my apprehension of it varies together with it. If its branches are bent or broken my perceptions vary accordingly. Further knowledge, however, reveals that the perception depends not only upon the tree but also upon particular parts of the ‘self,’ namely upon the sense-organs, nerves and brain. Experience reveals these relations of dependence just as it reveals the tree. When the causal series between the tree and the brain-state is not completed, when, for instance, it is interrupted by injury to the nerve-fibres, the self can have no apprehension of the tree. The perception depends, therefore, only mediately on the object, and immediately on changes in the nervous system. And the relative point of view therefore reveals three relations of dependence: (1) between the tree and its perception; (2) between the tree and the nervous system; (3) between the nervous system and the perception. For all three the same formula holds: if the first term be changed the second undergoes corresponding changes. But only in form (2) is the relation causal or physical, and so a special case of the law of the conservation of energy. The two other forms (1 and 3) are logical functional relations.
Much of Avenarius’ best work has consisted in developing a new view of the nature both of mental and of physiological processes, and so in restating the parallelist theory in a thoroughly original manner. He was dissatisfied with the use made by the traditional psychology of the distinction between knowing, feeling and willing, and also with the mental atomism of the associationists. The fundamental characteristic of the mental life is, he holds, that it falls into more or less distinguishable series which in their general features are of a fixed and universal type. Each series originates in a feeling of pain, opposition, or uncertainty. The mind then desires or strives or wills to remove this unpleasant experience; and as a consequence the series of mental experiences sooner or later, through complex mental processes or through simple habitual actions, as the case may be, terminates in the feeling of rest, successful action, and certainty. “We feel lightened and exalted, satisfied and freed.” Such series, which are repeated as often as mental experience occurs, Avenarius has named ‘vital series’.
Avenarius conceives the brain-processes as being of an
