William Lyon Phelps speech on The Pleasure of Books
The habit of reading is one of the greatest resources of mankind; and we enjoy reading books that belong to us much more than if they are borrowed. A borrowed book is like a guest in the house; it must be treated with punctiliousness, with a certain considerate formality. You must see that it sustains no damage; it must not suffer while under your roof. You cannot leave it carelessly, you cannot mark it, you cannot turn down the pages, you cannot use it familiarly. And then, some day, although this is seldom done, you really ought to return it.
But your own books belong to you; you treat them with that affectionate intimacy that annihilates formality. Books are for use, not for show; you should own no book that you are afraid to mark up, or afraid to place on the table, wide open and face down. A good reason for marking favorite passages in books is that this practice enables you to remember more easily the significant sayings, to refer to them quickly, and then in later years, it is like visiting a forest where you once blazed a trail. You have the pleasure of going over the old ground, and recalling both the intellectual scenery and your own earlier self.
Everyone should begin collecting a private library in youth; the instinct of private property, which is fundamental in human beings, can here be cultivated with every advantage and no evils. One should have one's own bookshelves, which should not have doors, glass windows, or keys; they should be free and accessible to the hand as well as to the eye...