While I believe all the foregoing suggestions are judicious and necessary, I am willing to admit that their wisdom may reasonably be doubted. But there is one practice about which there can be no controversy—that of making sure you thoroughly understand every idea of an author. While most people will not verbally contradict this advice, their actual practice may be a continual contradiction of it. They will be in such haste to finish a book that they will not stop to make sure they really understand the more difficult or obscure passages. Just what they hope to gain it is difficult to say. If they think it is wasting time to try to understand every idea, it is surely a greater waste of time to read an idea without understanding it. To be sure, the difficulty of understanding may be the fault of the author. It may be due to his involved and muddled way of expressing himself. It may be the vagueness of the idea itself. But if anything this is all the greater reason why you should attempt to understand it. It is the only way you can find whether or not the author himself really knew what he was talking about. To understand thoroughly the thought of another does not necessarily mean to sympathize with it; it does not mean to ask how that other came by it. It means merely to substitute as far as possible concrete mental images for the words he uses, and analyze those images to discover to what extent they agree with facts. Better to carry this out, you might follow another practice of immense value. Whenever you are puzzled as to an author’s meaning, or whenever you do not care to accept his solution of a problem but are undecided as to what the solution is, or whenever you want to carry an idea further than he has, or above all, whenever an original and important relevant thought is suggested to you, you should take your eyes from your book—shut it if necessary—and let your thinking flow on; give it fair play, even if it takes an hour before your vein of suggested thought exhausts itself. Of course this practice will prevent you from finishing a book as soon as you otherwise would. And if finishing a book be your aim, I have nothing to say. But if your end is to attain true, sound knowledge, knowledge which you will retain; if your object is to become a thinker, the practice will prove of unspeakable benefit. It will not interfere with concentration. Remember your object is to concentrate primarily on the subject, not on the book; you intend to become a thinker, not an interpreter or a commentator or a disciple of any author.