A person may have discovered some portion of truth or wisdom, after spending a great deal of time and trouble in thinking it over for himself and adding thought to thought; and it may sometimes happen that he could have found it all ready to hand in a book and spared himself the trouble. But even so, it is a hundred times more valuable if he has acquired it by thinking it out for himself. For it is only when we gain our knowledge in this way that it enters as an integral part, a living member, into the whole system of our thought; that it stands in complete and firm relation with what we know; that it is understood with all that underlies it and follows from it; that it wears the color, the precise shade, the distinguishing mark, of our own way of thinking; that it comes exactly at the right time, just as we felt the necessity for it; that it stands fast and cannot be forgotten.