How to Read a Book: The Classic Guide to Intelligent Reading by Charles van Doren Page B

categories, and most people could probably place most books in the right category if they thought about it. But not all books in all categories.
    The trouble is that as yet we have no principles of classification. We will have more to say about these principles as we proceed in our discussion of the higher levels of reading. For the moment, we want to confine ourselves to one basic distinction, a distinction that applies across the board to all expository works. It is the distinction between theoretical and practical works.
    Practical vs. Theoretical Books
    Everyone uses the words "theoretical" and "practical," but not everyone knows what they mean, perhaps least of all the hardheaded practical man who distrusts all theorists, especially if they are in the government. For such persons, "theoretical" means visionary or even mystical; "practical'' means something that works, something that has an immediate cash return. There is an element of truth in this. The practical has to do with what works in some way, at once or in the long run. The theoretical concerns something to be seen or understood. If we polish the rough truth that is here being grasped, we come to the distinction between knowledge and action as the two ends a writer may have in mind.
    But, you may say, in dealing with expository books, are we not dealing with books that convey knowledge? How does action come into it? The answer, of course, is that intelligent action depends on knowledge. Knowledge can be used in many ways, not only for controlling nature and inventing useful machines or instruments but also for directing human conduct and regulating man's operations in various fields of skill. What we have in mind here is exemplified by the distinction between pure and applied science, or, as it is sometimes very inaccurately expressed, between science and technology.
    Some books and some teachers are interested only in the knowledge itself that they have to communicate. This does not mean that they deny its utility, or that they insist that knowledge is good only for its own sake. They simply limit themselves to one kind of communication or teaching, and leave the other kind to other men. These others have an interest beyond knowledge for its own sake. They are concerned with the problems of human life that knowledge can help to solve.
    They communicate knowledge, too, but always with a view to and an emphasis upon its application.
    To make knowledge practical we must convert it into rules of operation. We must pass from knowing what is the case to knowing what to do about it if we wish to get somewhere. This can be summarized in the distinction between knowing that and knowing how. Theoretical books teach you that something is the case. Practical books teach you how to do something you want to do or think you should do.
    This book is practical, not theoretical. Any guidebook is a practical book. Any book that tells you either what you should do or how to do it is practical. Thus you see that the class of practical books includes all expositions of arts to be learned, all manuals of practice in any field, such as engineering or medicine or cooking, and all treatises that are conveniently classified as moral, such as books on economic, ethical, or political problems. We will later explain why this last group of books, properly called "normative," constitutes a very special category of practical books.
    Probably no one would question our calling expositions of arts to be learned and manuals or rule books, practical works.
    But the "practical" man to whom we have referred might object to the notion that a book on ethics, say, or one on economics, was practical. He might say that such a book was not practical because it was not true or would not work.
    In fact, this is irrelevant to the point, although a book about economics that is not true is a bad book. 'Strictly speaking, any ethical work teaches us how to live our lives, tells us what we should do and not do,