that he stirs our emotions, and works up his unrealities into something resembling a poem.  It is not primarily his task to please, as it is not the task of the serious worker in science to please those whom he is called upon to instruct.  Truth is truth, whether it be scientific truth or philosophical truth.  And error, no matter how agreeable or how nicely adjusted to the temper of the times, is always error.  If it is error in a field in which the detection and exposure of error is difficult, it is the more dangerous, and the more should we be on our guard against it.

We may, then, accept the lesson of the history of philosophy, to wit, that we have no right to regard any given doctrine as final in such a sense that it need no longer be held tentatively and as subject to possible revision; but we need not, on that account, deny that philosophy is, what it has in the past been believed to be, an earnest search for truth.  A philosophy that did not even profess to be this would not be listened to at all.  It would be regarded as too trivial to merit serious attention.  If we take the word “science” in the broad sense to indicate a knowledge of the truth more exact and satisfactory than that which obtains in common life, we may say that every philosophy worthy of the name is, at least, an attempt at scientific knowledge.  Of course, this sense of the word “science” should not be confused with that in which it has been used elsewhere in this volume.

87.  HOW TO READ THE HISTORY OF PHILOSOPHY.—­He who takes up the history of philosophy for the first time is apt to be impressed with the fact that he is reading something that might not inaptly be called the history of human error.

It begins with crude and, to the superficial spectator, seemingly childish attempts in the field of physical science.  There are clever guesses at the nature of the physical world, but the boldest of speculations are entered upon with no apparent recognition of the difficulty of the task undertaken, and with no realization of the need for caution.  Somewhat later a different class of problems makes its appearance—­the problems which have to do with the mind and with the nature of knowledge, reflective problems which scarcely seem to have come fairly within the horizon of the earliest thinkers.

These problems even the beginner may be willing to recognize as philosophical; but he may conscientiously harbor a doubt as to the desirability of spending time upon the solutions which are offered.  System rises after system, and confronts him with what appear to be new questions and new answers.  It seems as though each philosopher were constructing a world for himself independently, and commanding him to accept it, without first convincing him of his right to assume this tone of authority and to set up for an oracle.  In all this conflict of opinions where shall we seek for truth?  Why should we accept one man as a teacher rather than another?  Is not the lesson to be gathered from the whole procession of systems best summed up in the dictum of Protagoras:  “Man is the measure of all things”—­each has his own truth, and this need not be truth to another?