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, and cannot simply put them aside.
(3) The peculiar difficulties of reflective thought may account for the fact that these sciences are, more than others, a field in which we may expect to find disputes and differences of opinion.
(4) We need not be afraid that the whole field of human knowledge will come to be so divided up into special sciences that philosophy will disappear.

The problems with which the philosopher occupies himself are real problems, which present themselves unavoidably to the thoughtful mind, and it is not convenient to divide these up among the several sciences.

This will become clearer as we proceed.
[1] "First Principles," Part II, section 37..