Take psychology as an instance. How does it happen that the physicist
calmly develops his doctrine without finding it necessary to make his
bow to philosophy at all, while the psychologist is at pains to explain
that his book is to treat psychology as "a natural science," and will
avoid metaphysics as much as possible? For centuries men have been
interested in the phenomena of the human mind. Can anything be more
open to observation than what passes in a man's own consciousness?
Why, then, should the science of psychology lag behind? and why these
endless disputes as to whether it can really be treated as a "natural
science" at all?

Again. May we assume that, because certain disciplines have taken a
position of relative independence, therefore all the rest of the field
will surely come to be divided up in the same way, and that there will
be many special sciences, but no such thing as philosophy? It is hasty
to assume this on no better evidence than that which has so far been
presented. Before making up one's mind upon this point, one should
take a careful look at the problems with which the philosopher occupies
himself.

A complete answer to the questions raised above can only be given in
the course of the book, where the main problems of philosophy are
discussed, and the several philosophical sciences are taken up and
examined. But I may say, in anticipation, as much as this:--

(1) Philosophy is reflective knowledge. What is meant by reflective
knowledge will be explained at length in the next chapter.

(2) The sciences which are grouped together as philosophical are those
in which we are forced back upon the problems of reflective thought,