david deutsch addresses johnson's objection to idealism in "the fabric of reality" when he states that, if we judge the value of our mental images of the world by the quality and quantity of the sense data that they can explain, then the most valuable mental image—or theory—that we currently have is that the world has a real independent existence and that humans have successfully evolved by building up and adapting patterns of mental images to explain it. this is an important idea in scientific thought.