Books are for reading, but man must bring to their reading a desire to learn and a power of absorbing. Reading should be active, not passive. (79)When students first go to a library, they may be at a loss as to what to read of all the different subjects. Well, Bacon tells you to 'look at weak places in your armor(盔甲)', and shows you how to fill up the blanks in your knowledge. On the other hand, it is no good just trying to fill your mind with knowledge. Knowledge in itself is often useless. A mind filled with too much knowledge is like a room too full of furniture a man cannot walk about freely in it, and look out the windows. It is much better to concentrate on a few subjects which interest you and to deal lightly with the others than to march heavily through the whole range(范围) of learning, like a silly tourist going through a museum and not missing a single object. (80) If you try to master every subject, you may become very wise, but you will be very lonely and you will probably lose all your friends. So you must learn to pick and choose, and you must also learn to look here and there in a library like a camel eating grass on the grassland. If you watch it eating, you will see that although he is supposed to be one of the most stupid animals in the world, he has at least one of the qualities(品质) of the cultured(有修养的) man, the power to pick and choose. A student looking for mental food in a library should take the camel as his model. The writer thinks that one must ______