“Water is fluid, soft, and yielding. But water will wear away rock, which is rigid and cannot yield. As a rule, whatever is fluid, soft, and yielding will overcome whatever is rigid and hard. This is another paradox: what is soft is strong.” –Lao-Tzu (600 B.C.)
Rivers demand this to be true.
*Photo is of Little Carp River, Porcupine Mountains, Upper Peninsula, Michigan