Most people can swim a narrow river. Water is an alien element, but with labor we can force ourselves through it. A good swimmer can cross a wide river, a lake, even the English Channel; no one, as far as we know, has ever swum the Atlantic Ocean, or is likely to do so. Even a champion swimmer, if he had business which required to spend alternate weeks in Paris and London, would not make the trip regularly by swimming the English Channel. Although we can force ourselves through water by skill and main strength, for all practical purposes our ability to traverse water is only as good as our ships or our airplanes. And so with the activities of our brains. Thinking is probably as foreign to human nature as is water; it is an unnatural element into which we throw ourselves with hesitation, and in which we flounder once we are there. We have learned, during the millenniums, to do rather well with thinking, but only if we buoy ourselves up with words. Some thinking of a simple sort we can do without words, but difficult and sustained thinking, presumably, is completely impossible without their aid, as traversing the Atlantic Ocean is presumably impossible without instruments or supramarine transportation.