If， when you've finished reading a book， the pages are filled with your notes， you know that you read actively. The most famous active reader of great books I know is President Hutchins， of the University of Chicago. He also has the hardest schedule of business activities of any man I know. He invariably read with pencil， and sometimes， when he picks up a book and pencil in the evening， he finds himself， instead of making intelligent notes， drawing what he calls " caviar factories" on the margins. When that happens， he puts the book down. He knows he's too tired to read， and he's just wasting time.

    But， you may ask， why is writing necessary？ Well， the physical act of writing， with your own hand， brings words and sentences more sharply before your mind and preserves them better in your memory. To set down your reaction to important words and sentences you have read， and the questions they have raised in your mind， is to preserve those reactions and sharpen those questions. You can pick up the book the following week or year， and there are all your points of agreement， disagreement， doubt and inquiry. It's like resuming an interrupted conversation with the advantage of being able to pick up where you left off.

    And that is exactly what reading a book should be： a conversation between you and the author. Presumably he knows more about the subject than you do； naturally you'll have the proper humility as you approach him. But don't let anybody tell you that a reader is supposed to be solely on the receiving end. Understanding is a two-way operation； learning doesn't consist in being an empty receptacle. The learner has to question himself and question the teacher. He even has to argue with the teacher， once he understands what the teacher is saying. And marking a book is literally an expression of your differences， or agreements of opinion， with the author.

    There are all kinds of devices for marking a book intelligently and fruitfully. Here's the way I do it：

    1. Underlining： of major points， of important or forceful statements.

    2. Vertical lines at the margin： to emphasize a statement already underlined.

    3. Star， asterisk， or other doo-dad at the margin： to be used sparingly， to emphasize the ten or twenty most important statements in the book.

    4. Numbers in the margin： to indicate the sequence of points the author makes in developing a single argument.

    5. Number of other pages in the margin： to indicate where else in the book the author made points relevant to the point marked； to tie up the ideas in a book， which， though they may be separated by many pages， belong together.

    6. Circling of key words or phrases.

    7. Writing in the margin， or at the top or bottom of the page， for the sake of： recording questions （and perhaps answers） which a passage raise in your mind； reducing a complicated discussion to a simple statement； recording the sequence of major points right through the book. I use the end-papers at the back of the book to make a personal index of the author's points in the order of their appearance. The front end-papers are， to me， the most important. Some people reserve them for a fancy bookplate， I reserve them for fancy thinking. After I have finished reading the book and making my personal index on the back end-papers， I turn to the front and try to outline the book， not page by page， or point by point （I've already done that at the back）， but as an integrated structure， with a basic unity and an order of parts. This outline is， to me， the measure of my understanding of the work.

    Phrases & Expressions

    read between the lines（fig.） find more meaning than the words appear to express 体会字里行间的言外之意