When you stop to think, the whole idea of comprehension has a faintly archaic taste, like the sound of forgotten tongues or a look into a Victorian camera obscura. We Americans are much higher on simple understanding. It makes it easier to read the billboards when you're heading into town on the expressway at plus-fifty. To comprehend, the mental jaws have to gape wide enough to make the tendons creak. Understanding, however, can be purchased on every paperback-book rack in America.