critically asked reality is still attributed to objects which lie outside of experience, but great emphasis is laid upon the subjective factor in knowledge. It is taken for granted that perception does not give an object as it really is, that the whole content is not given in perception, but, on the other hand, it is assumed that the whole content given in perception does not really belong to the object. Objective reality is thus, at the same time, more and less than experience.
The original question, How is the world constituted? demands now a distinction between what can be taken as valid experience of objects and experience which misrepresents its objects. By this emphasis laid upon the problem of knowledge, and the recognition that the mind is so constituted as perhaps to interfere with its own cognitive purposes, psychology becomes of decided importance for philosophy, and it is not long before the world of real objects shrinks to a region of things in themselves, set over against forms of experience. It is a matter of recent history how the content of the world, which seemed to be lost on the objective side, was brought back from the subjective side, and how from this point of view the great systems of idealism grew up. But whether deservedly or not, those systems have fallen into disrepute, one factor in this situation being the progress of physical science. And to-day if one asks how we know the world, the scientist will point to his instruments for observation and experiment and say, * With these we know the world.'
But knowledge secured by the aid of instruments for exact measurement is not the less subjective. Truer, perhaps, it would have been to say, 'By the use of these instruments do we conceive the world.'
The question, How is the world constituted? has become, provisionally at least, the question, How is the world conceived! And to this question one may now give a somewhat unexpected answer. The world is conceived by a nervous organism reacting in a certain way to its environment, and the question, How is the world conceived! becomes the question. How does this organism behave in conceiving the world? or, "What kind of a natural process is philosophy! Philosophy is a certain type of human activity, and if one agrees that activities of thought depend upon processes in nervous tissue, one has a ground for asking, as a scientist, what sort of natural process philosophy is.
Avenarius undertakes to carry out frankly the psychophysical point of view. He conceives that types of experience depend upon typical processes within an organ. The organ he afterwards called by the name of 'System C' and its processes he sought to describe as 'Vital Series.'
