" Dad would haul down a book and we’d look it up. Then he would try four or five more with other opinions. Dad doesn’t hold with the idea that it-must-be-true-or-they-wouldn’t-have-printed-it; he doesn’t consider any opinion sacred—it shocked me the first time he took out a pen and changed something in one of my math books. "

― Robert A. Heinlein , Have Space Suit—Will Travel