The interest in the history of philosophy is certainly not a diminishing one.  Text-books covering the whole field or a part of it are multiplied; extensive studies are made and published covering the work of individual philosophers; innumerable historical discussions make their appearance in the pages of current philosophical journals.  No student is regarded as fairly acquainted with philosophy who knows nothing of Plato and Aristotle, Descartes and Spinoza, Berkeley and Hume, Kant and Hegel, and the rest.  We should look upon him as having a very restricted outlook if he had read only the works of the thinkers of our own day; indeed, we should not expect him to have a proper comprehension even of these, for their chapters must remain blind and meaningless to one who has no knowledge of what preceded them and has given birth to the doctrines there set forth.

It is a fair question to ask:  Why is philosophy so bound up with the study of the past?  Why may we not content ourselves with what has up to the present been attained, and omit a survey of the road along which our predecessors have traveled?

84.  THE ESPECIAL IMPORTANCE OF HISTORICAL STUDIES TO REFLECTIVE THOUGHT.—­In some of the preceding chapters dealing with the various philosophical sciences, it has been indicated that, in the sciences we do not regard as philosophical, men may work on the basis of certain commonly accepted assumptions and employ methods which are generally regarded as trustworthy within the given field.  The value both of the fundamental assumptions and of the methods of investigation appear to be guaranteed by the results attained.  There are not merely observation and hypothesis; there is also verification, and where this is lacking, men either abandon their position or reserve their judgment.

Thus, a certain body of interrelated facts is built up, the significance of which, in many fields at least, is apparent even to the layman.  Nor is it wholly beyond him to judge whether the results of scientific investigations can be verified.  An eclipse, calculated by methods which he is quite unable to follow, may occur at the appointed hour and confirm his respect for the astronomer.  The efficacy of a serum in the cure of diseases may convince him that work done in the laboratory is not labor lost.

It seems evident that the several sciences do really rise on stepping stones of their dead selves, and that those selves of the past are really dead and superseded.  Who would now think of going back for his science to Plato’s “Timaeus,” or would accept the description of the physical world contained in the works of Aristotle?  What chemist or physicist need busy himself with the doctrine of atoms and their clashings presented in the magnificent poem of Lucretius?  Who can forbear a smile—­a sympathetic one—­when he turns over the pages of Augustine’s “City of God,” and sees what sort of a world this remarkable man believed himself to inhabit?