We shall assume that what each man does is based not on direct and certain knowledge, but by pictures made by himself or given to him. If his atlas tells him the world is flat he will not sail near what he believes to be the edge of our planet for fear of falling off. If his maps include a fountain of eternal youth, a Ponce de Leon will go off in quest of it. If someone digs up yellow dirt that looks like gold, he will for a time act exactly as if he has found gold. The way in which the world is imagined determines at any particular moment what men will do. It does not determine what they will achieve. It determines their effort, their feelings, their hopes, not their accomplishments and results.